Based on the 1990 USDA Hardiness Zone Map, this interactive version covers the state of Hawaii which ranges from USDA Zone 10a to USDA Zone 11a. The annual extreme minimum temperature is a useful indicator, but ultimately only one factor among many for plant growth and survival. Tulips for example, can be planted in as low as Zone 4. The 2012 USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. Drawbacks. Navigate the map. The hardiness scales do not take into account the reliability of snow cover in the colder zones. Hardiness.zone. Easy to grow…, Over 200 Gardenia varieties are available in a wide range of height, flower size and color, leaf size and color, blooming time and duration and shrub habit. You can then choose plants that are suggested for that USDA zone. [21] The cooler UK summers must be considered. [15] They are numerically about 6 lower than the USDA system. X₇ = maximum wind gust in (km/hr) in 30 years. The Mediterranean Sea acts as a temperature regulator, so this area is generally warmer than other parts of the continent; except in mountainous areas where the sea effect lowers, it belongs in zones 8–10; however, southern Balkans (mountainous Western and Eastern Serbia, continental Croatia, and Bulgaria) are colder in winter and are in zones 6–7. Other hardiness rating schemes have been developed as well, such as the UK Royal Horticultural Society and US Sunset Western Garden Book systems. Click on the map to display a pop-up window with the plant hardiness zone, average temperature, and temperature range. [citation needed], Sunset publishes a series that breaks up climate zones more finely than the USDA zones, identifying 45 distinct zones in the US, incorporating ranges of temperatures in all seasons, precipitation, wind patterns, elevation, and length and structure of the growing season. The 2012 USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. Conversely, Fort Yukon, Alaska has the coldest hardiness zone for any city in the United States at 1a. across (7-12 cm). The west coast of Sweden (Gothenburg and southwards) enjoys particularly mild winters and lies in zone 7, therefore being friendly to some hardy exotic species (found, for example, in the Gothenburg Botanical Garden), the southeast coast of Sweden has a colder winter due to the absence of the Gulf Stream. Sydney residents are split between zones 3a and 4b. The 2012 USDA Hardiness Zone Map Move your mouse over the map to zoom in for a closer look at your area. Considered the standard measure of plant hardiness, the USDA Plant Hardiness Zone Map is based on average annual minimum winter temperatures. The map is divided into thirteen distinct 10ºF zones, which are further divided into sub-zones of 5°F. Unless otherwise specified, "hardiness zone" or simply "zone" usually refers to the USDA scale. Their map purported to show finer detail, for example, reflecting urban heat islands by showing the downtown areas of several cities (e.g., Baltimore, Maryland; Washington, D.C. and Atlantic City, New Jersey) as a full zone warmer than outlying areas. Hawaii Interactive 1990 USDA Hardiness Zone Map. For example, Australian zone 3 is roughly equivalent to USDA zone 9. The US Hardiness Zones . The first map was issued in 1960, and revised in 1965. It used uniform 10-degree Fahrenheit ranges, and gradually became widespread among American gardeners.[3][4]. Vigorous, Hibiscus coccineus (Scarlet Rose Mallow) is a woody-based perennial noted for its 5-petaled, bright crimson red flowers, up to 3-5 in. If you see a hardiness zone in a gardening catalog or plant description, chances are it refers to this USDA map. An extreme example of a cold sink is Funtensee, Bavaria which is at least in zone 3 and maybe even in zone 1 or 2. Location Hardiness Zone; Adana: Buy shrubs, bushes for plant hardiness zone 11. [32], Geographical regions defined by climatic conditions for horticultural purposes. [16], Owing to the moderating effect of the North Atlantic Current on the Irish and British temperate maritime climate, Britain, and Ireland even more so, have milder winters than their northerly position would otherwise afford. Get USDA Plant Hardiness Zone essential facts. Many zone boundaries were changed as a result of the more recent data, as well as new mapping methods and additional information gathered. Shop; Specials; About; Resources; Contact Us; Gift Cards; Sign Up For Our Newsletter; ‹ Continue Shopping Secure Checkout Find your garden’s hardiness zone by Zip Code.. Gardeners rely on USDA Hardiness Zone Maps to tell us which plants survive and thrive locally. Unless specifically noted, all zones in this section are USDA zones. Landscapers in our local area know that they could use a plant hardy to Zone 7 (-17.8C) without fear of it perishing in the winter cold. [16] This index comes from a formula originally developed by Ouellet and Sherk in the mid-1960s. The spread of weather stations may be insufficient and too many places with different climates are lumped together. Fagus sylvatica. The southern middle portion of the mainland and central coastal areas are in the middle zones (zones 8, 7, and 6). Learn how and when to remove this template message, "History of Plant Hardiness Zone Maps – The Rest of the Story", "New arborday.org Hardiness Zone Map reflects warmer climate : Latest hardiness zones, based on most current temperature data available, suggest up-to-date choices for best trees to plant", "What's New | USDA Plant Hardiness Zone Map", "Beyond Traditional Hardiness Zones: Using Climate Envelopes to Map Plant Range Limits", "Die Wärmezonen der Erde, nach der Dauer der heissen, gemässigten und kalten Zeit und nach der Wirkung der Wärme auf die organische Welt betrachtet [The thermal zones of the Earth according to the duration of hot, moderate and cold periods and of the impact of heat on the organic world]", "Natural Resources Canada – Plant Hardiness of Canada", "Woody Ornamental Plant Zonation: III. The hardiness category is indicated for each individual plant species. Europe Hardiness Zone Map has a variety pictures that aligned to locate out the most recent pictures of Europe Hardiness Zone Map here, and then you can acquire the pictures through our best europe hardiness zone map collection.Europe Hardiness Zone Map pictures in here are posted and uploaded by secretmuseum.net for your europe hardiness zone map images collection. The Croatian (Dalmatian) coast, Albania, and northern Greece are in zones 8–9, as are central-northern Italy (hills and some spots in Po Valley are however colder) and southern France; Central Iberia is 8–9 (some highland areas are slightly colder). Owing to its position in the Atlantic, its latitude and the effects of the Gulf Stream, the European Macaronesia has by far the warmest winters out of any place in Europe. Keep in mind that local variations such as moisture, soil, winds, and other conditions might affect the viability of individual plants. It consists of three archipelagos, the Portuguese Azores and Madeira, belonging to zones 11a/11b and 11b/12a respectively and the Spanish Canary Islands, part of zones 12a/12b. The first attempts to create a geographical hardiness zone system were undertaken by two researchers at the Arnold Arboretum in Boston: the first was published in 1927 by Alfred Rehder,[1] and the second by Donald Wyman in 1938. These examples prove that local topography can have a pronounced effect on temperature and thus on what is possible to grow in a specific region. Related Turkey Maps: List of Hardiness Zones for Locations in Turkey . In the United States, most of the warmer zones (zones 9, 10, and 11) are located in the deep southern half of the country and on the southern coastal margins. The warmer zones of the US, including zones 8, 10, 11, are in the southern half of the country and also the lower Pacific and Atlantic Coast while the cooler zones which include zones between 7 and 4 are on the northern and central parts of the country. Plant Hardiness Zones. USDA Plant Hardiness Zone Map. The criterion is the average number of days per year when the temperature exceeds 30 °C (86 °F). USDA zones 9 to 11 are areas with lowest temperatures at 25 to 40 degrees F. (-3-4 C.). USDA Plant Hardiness Zone at popflock.com Suitable hardiness means a plant can be expected to grow in the zone’s temperature extremes, as determined by the lowest average annual temperature. The hardiness of a plant is largely measured by how well it can withstand cold winter temperatures, so something that can survive the minimum temperature in Zone 5 would find Zone … The map excluded the detailed a/b half-zones introduced in the USDA's 1990 map, an omission widely criticized by horticulturists and gardeners due to the coarseness of the resulting map. The zones are defined by minimum temperature. [27] The Balkan area is also more prone to cold snaps and episodes of unseasonable warmth. United States hardiness zones (USDA scale), American Horticultural Society heat zones, Y = -67.62 + 1.734X₁ + 0.1868X₂ + 69.77X₃ + 1.256X₄+ 0.006119X₅ + 22.37X₆ - 0.01832X₇, "7a" areas not part of downtown Washington. Lithuania is in zones 5a, 5b, 6a, 6b, 7a and 7b. One is in zone 4a, one in zone 4b, and the other is in zone 5a. In Central Europe, the relevant zones decrease from zone 8 on the Belgian, Dutch, and German North Sea coast, with the exception of some of the Frisian Islands (notably Vlieland and Terschelling), the island of Helgoland, and some of the islands in the Rhine-Scheldt estuary, which are in zone 9, to zone 5 around Suwałki, Podlachia on the far eastern border between Poland and Lithuania. The southern European marker plant for climate as well as cultural indicator is the olive tree, which cannot withstand long periods below freezing so its cultivation area matches the cool winter zone. [8] The Canadian government publishes both Canadian and USDA-style zone maps. Hardiness zone 11: lowest average temperatures of 40°F to 50°F or 4.4°C to 10°C. Paperwhites are members of the daffodil family, Narcissus tazetta. across (12 cm), packed with star-shaped, pale yellow flowers adorned with a pale purple stripe down the center of each petal. In this method, common plants with known limits to their range are used. Browse photos of zone 11 landscaping and garden ideas by yard type, size, location, and feature. To figure out what corresponds to the USDA equivalent zone, simply take the average lowest temperature of the region and add 10 degrees for each higher zone. The U.S. zone 11 has an average lowest temperature of 40 degrees Fahrenheit (4 C.). However, in warm climates (zones 8-11) with hot, dry summers, paperwhite bulbs can be planted outside where they will bloom annually for many years. Lower zones can be found in Alaska (down to 1). New growth may be insufficient or fail to harden off affecting winter survival. In the Iberian Peninsula, parts of the southernmost zone of Spain in coastal Andalucía (parts of the provinces of Cádiz, Almería and Málaga) belong to zone 11a[26] as well as an area around Lagos and Vila do Bispo in the southwesternmost coastal strip of Portugal belong to zone 11a. Add USDA Plant Hardiness Zone to your PopFlock.com topic list or share. Zone 11 (40 to 50): Beets, mangos, begonias, and chives are especially productive in this zone. If you are planning to buy a shrub, perennial or tree, you need to make sure that this new plant will tolerate year-round conditions in your area. In addition to the USDA Hardiness zones there are American Horticultural Society (AHS) heat zones. [14] The Trewartha climate classification is often a good "real world" concept of climates and their relation to plants and their average growing conditions. The 1990 version of the USDA Plant Hardiness Zone Map included Canada and Mexico, but they were removed with the 2012 update to focus on the United States and Puerto Rico. About the USDA Hardiness Zones. The Åland Islands, as well as coastal southern Sweden, and the Stockholm area are in zone 7. It has been adapted by and to other countries (such as Canada) in various forms. woody • Europe • USDA 4 • 20 m • • ☆28 • Dryopteris filix-mas. The back of a packet of seeds tells you how much light, water and spacing a plant needs to grow and thrive. [2] The Arnold map was subsequently updated in 1951, 1967, and finally 1971, but eventually fell out of use completely. Often listed as zones 10 or 11 plants these are tropical plants used frequently as tender perennials, annuals, or seasonal tropical plants to … Climate variables that reflect the capacity and detriments to plant growth are used to develop an index that is mapped to Canada's Plant Hardiness Zones. The zones are defined by steps of 5 degrees Celcius, from −15–−10 °C for zone 1 to 15–20 °C for zone 7. Nov 4, 2019 - Explore Frank Quartey-Gyamfi's board "Plant hardiness zone 11" on Pinterest. Estonia is divided to warmer West and North coast (Tallinn 6a, Haapsalu 7b, Kärdla 7a, Kuressaare 7a, Paide 6a, Rakvere 6a, Narva 6a, Viljandi 6b) and colder inland (Tartu 5a, Valga 5a, Võru 5a). A hardiness zone is a geographic area defined to encompass a certain range of climatic conditions relevant to plant growth and survival. Coastal Ireland and Miami are both Zone 10, but have radically different insolation and summer heat and humidity. For example, zone 8 covers coastal, high latitude, cool summer locations like Seattle and London, as well as lower latitude, hot summer climates like Charleston and Madrid. In Sweden and Finland generally, at sea level to 500 metres (1,600 ft), zone 3 is north of the Arctic Circle, including cities like Karesuando, Pajala, and Rovaniemi. Plant hardiness zone 11 There are many other climate parameters that a farmer, gardener, or landscaper may need to take into account as well, such as humidity, precipitation, storms, rainy-dry cycles or monsoons, and site considerations such as soil type, soil drainage and water retention, water table, tilt towards or away from the sun, natural or manmade protection from excessive sun, snow, frost, and wind, etc. Reviewers noted the map zones appeared to be closer to the original USDA 1960 map in its overall zone delineations. Mount Isa has three climatic stations with more than a ten-year record. See more ideas about plant hardiness zone, plants, zone 11. Also, the plateaus and low mountain ranges in this region have a significant impact on how cold it might get during winter. There is a very small spot east of San Juan, Puerto Rico that includes the airport in coastal Carolina, where the mean minimum is 67 degrees F (19 C), which is classified as hardiness Zone 13b, the highest category, with temperatures rarely below 65 °F (18 °C). Below is a list of shrub names that normally succeed within zone eleven (11). The hardiness zones are developed by the Department of Agriculture in the United States. [20], USDA zones do not work particularly well in the UK as they are designed for a continental climate. The modern USDA system began at the US National Arboretum in Washington. [citation needed]. Zone 4 lies between the Arctic Circle and about 64–65°N, with cities such as Oulu and Jokkmokk, zone 5 (south to 61–62°N) contains cities such as Tampere, Umeå, and Östersund. The higher Australian zone numbers had no US equivalents prior to the 2012 addition by USDA of zones 12 and 13. Carolina, Puerto Rico has the warmest hardiness zone in the United States at 13b. Find your USDA zone using these state maps. Hardiness Zone 11 - Landscaping Ideas | YardShare.com YardShare Browse our guides to 11 to learn how to become a better gardener. The low latitude and often stable weather in Florida, the Gulf Coast, and southern Arizona and California, are responsible for the rarity of episodes of severe cold relative to normal in those areas. [citation needed]. The USDA Hardiness Zone Map divides North America into 11 separate planting zones; each growing zone is 10°F warmer (or colder) in an average winter than the adjacent zone. [8] The 2012 map was created digitally for the internet, and includes a ZIP Code zone finder and an interactive map.[9][10]. But, in Montreal, located to the southwest in zone 5, it is sometimes difficult to cultivate plants adapted to the zone because of the unreliable snow cover. [6], In 2012 the USDA updated their plant hardiness map based on 1976–2005 weather data, using a longer period of data to smooth out year-to-year weather fluctuations. Most of England, Wales and Scotland, parts of central Ireland, and, Most of western and southern England and Wales, western Scotland, also a very narrow coastal fringe on the east coast of Scotland and northeast England (within 5 km (3.1 mi) of the, Very low-lying coastal areas of the southwest of Ireland and the, This page was last edited on 5 March 2021, at 20:11. Higher zones can be found in Hawaii (up to 12) and Puerto Rico (up to 13). This evergreen shrub produces pretty, bicolor flowers followed by edible fruit. Obtain Plant Hardiness Zone Information. In addition, the zones do not incorporate any information about summer temperature or insolation; thus sites which may have the same mean winter minima, but markedly different summer temperatures, will be accorded the same hardiness zone. [5], In 2006, the Arbor Day Foundation released an update of U.S. hardiness zones, using mostly the same data as the AHS. Farmers, gardeners, and landscapers in the former two must plan for entirely different growing seasons from those in the latter. The 2003 map placed many areas approximately a half-zone higher (warmer) than the USDA's 1990 map. Latvia's capital Riga is in zone 6a. Whilst the USDA system of plant hardiness zones is well adopted across the world, it’s … The Spanish and Portuguese Atlantic coast, much of Andalusia and Murcia, coastal and slightly inland southern Valencian Community, a part of coastal Catalonia, the Balearic Islands, southwestern Sardinia, most of Sicily, coastal southern Italy, some areas around Albania,[24][25] coastal Cyprus and southwestern Greece are in zone 10. Listed alphabetically by Scientific name first and common name second. Botanical name Type Origin Zone Height Flower Points Search; Sort by. [22] The RHS hardiness ratings are based on absolute minimum winter temperatures (in °C) rather than the long-term average annual extreme minimum temperatures that define USDA zones.[22]. The USDA map was revised and reissued in 1990 with freshly available climate data, this time with 5-degree distinctions dividing each zone into new "a" and "b" subdivisions. For instance, despite having similar daily means and temperature amplitudes to Nantucket, Massachusetts for each month, Sarajevo has recorded below-freezing temperatures in every month of the year.[28][29]. Blooming from mid-summer to early fall, the eye-catching flowers are adorned with conspicuous, protruding, creamy-white to pale yellow tubes of stamens. USDA Agricultural Research Service (USDA-ARS) website. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones. The USDA hardiness zones are not used in Australia. Often we are asked by PLANTS users about the USDA Plant Hardiness Zone Map, but neither PLANTS/ NPDT, nor the USDA NRCS as a whole, are responsible for this map. Plant name: Filter. As an example, Quebec City in Canada is located in zone 4, but can rely on a significant snow cover every year, making it possible to cultivate plants normally rated for zones 5 or 6. Hailing from the temperate shores of the southeastern Mediterranean, these bright, peppery-scented bulb flowers are not winter hardy. For example, a plant may be described as "hardy to zone 10": this means that the plant can withstand a minimum temperature of 30 °F (−1.1 °C) to 40 °F (4.4 °C). The Faroe Islands, at 62–63°N are in zone 8, as are the outer Lofoten Islands at 68°N. Shop; Specials; About; Resources; Contact Us; Gift Cards; Sign Up For Our Newsletter; ‹ Continue Shopping Secure Checkout Select Page. This extremely warm zone features mellow winters with an average minimum winter temperature of between 40 to 50 degrees F. Cold hardiness is not a factor in this zone, since it has zero frost days. This map shows higher zones than the accepted USDA map allows for—the USDA hardiness map simply assigns Zone 11 for anywhere with an average annual minimum temperature above 40 F. If they are following the zone system, then each zone is 10 F higher than the last one, making Zone 12 at 50 F and Zone 13 at 60 F. 10 of 11 For plants in pots, you need to reduce the zone by two points, as potted plants freeze quicker than … The country is in zones 5a, 5b, 6a, 6b, 7a and 7b. As an extreme example, due to the Gulf stream most of the United Kingdom is in zones 8–9, while in the US, zones 8–9 include regions such as the subtropical coastal areas of the southeastern US and Mojave and Chihuahuan inland deserts, thus an American gardener in such an area may only have to plan for several nights of cold temperatures per year, while their British counterpart may have to plan for several months. [9][3][12], An alternative means of describing plant hardiness is to use "indicator plants". This means that the USDA hardiness zones relevant to Britain and Ireland are quite high, from 7 to 10, as shown below. Snow acts as an insulator against extreme cold, protecting the root system of hibernating plants. The islands of Malta, Lampedusa, a few areas on the southernmost coast of Cyprus all belong to zone 11a[citation needed]. [13], In addition, the Köppen climate classification system can be used as a more general guide to growing conditions when considering large areas of the Earth's surface or attempting to make comparisons between different continents. But even without these gorgeous blooms, this plant is worth growing for its shiny, palmately divided, deep green leaves. The original and most widely used system, developed by the United States Department of Agriculture (USDA) as a rough guide for landscaping and gardening, defines 13 zones by annual extreme minimum temperature. Many areas were a half zone warmer than the previous 1990 map. Scandinavia lies at the same latitude as Alaska or Greenland, but the effect of the warm North Atlantic Current is even more pronounced here than it is in Britain and Ireland. Based on the minimum ten-year average winter temperatures, plant hardiness zones maps have been progressively developed, first by the Department of Agriculture (USDA) for the United States and then more or less applied to the rest of the planet. Warm region gardeners are often frustrated by their inability to grow many types of plants that are not hardy in their zone. The map has a higher resolution than previous ones, and is able to show local variations due to things such as elevation or large bodies of water. [8] Research in 2016 suggests that USDA plant hardiness zones will shift even further northward under climate change. Therefore, to ensure your new acquisition will survive and grow year after year, you will need to compare the hardiness zone of your area with the hardiness zone of your plant (included in most American references books, nursery catalogs and…, Pseudogynoxys chenopodioides (Mexican Flame Vine) is an attractive evergreen vine with fleshy, arrowhead-shaped leaves and large clusters of brilliant flowers over a long season. Zone information alone is often not adequate for predicting winter survival, since factors such as frost dates and frequency of snow cover can vary widely between regions. The range of minimum average temperatures for zone 13 is between 60°F and 70°F or +15.6°C and +21.1°C. [31], The USDA map published in 2012 shows that most of the US has become a half zone (5 °F) hotter in winter compared to the 1990 release. Zone 12 (50 to 60): Grow crops like summer squash, hot pepper, borage, and heliconia if you live in Zone … Different locations in the same city are suitable for different plants. Kiruna is the major exception here, which being located on a hill above frost traps, is in zone 5. Only 738 Australian stations have records of more than ten years (one station per 98,491 hectares or 243,380 acres), though more populated areas have relatively fewer hectares per station. The Australian National Botanic Gardens have devised another system more in keeping with Australian conditions. Custom programming and server maintenance by Reinvented Inc.. Connect With Us The foliage of long, grasslike, basal bright green leaves emerges in late winter and dies back as the flowers appear. That means a freeze is rare and daytime temperatures are warm even in winter. Save for a very small spot near Karasjok, Norway, which is in zone 2, nowhere in the Arctic part of Scandinavia does it get below zone 3. The far northern portion on the central interior of the mainland have some of the coldest zones (zones 5, 4, and small area of zone 3) and often have much less consistent range of temperatures in winter due to being more continental, and thus the zone map has its limitations in these areas. In 2003, the American Horticultural Society (AHS) produced a draft revised map, using temperature data collected from July 1986 to March 2002. This information is based on a USDA standard, called hardiness zones , which considers the environmental conditions that plants need to thrive in certain locations. Many plants may survive in a locality but will not flower if the day length is insufficient or if they require vernalization (a particular duration of low temperature). Acca sellowiana (syn. The map is produced by the U.S. Department of Agriculture (USDA) Agricultural … The USDA Plant Hardiness Zone Map is a valuable agricultural and horticultural reference. [30], South Africa has five horticultural or climatic zones. The warmest zone in the 48 contiguous states is the Florida Keys (11b) and the coldest is in north-central Minnesota (3a). The latest version of the USDA Zone Map was jointly developed by USDA's Agricultural Research Service (ARS) and Oregon State University's (OSU) PRISM Climate Group, … Generally speaking, the hardiness zones are high considering the latitude of the region, although not as high as Northern Europe with the Shetland Islands where zone 9 extends to over 60°N. Even the extreme minimum itself may not be useful when comparing regions in widely different climate zones. Another notable example is Waksmund, a small village in the Polish Carpathians, which regularly reaches −35 °C (−31 °F) during winter on calm nights when cold and heavy airmasses from the surrounding Gorce and Tatra Mountains descend down the slopes to this low-lying valley, creating extremes which can be up to 10 °C (18 °F) colder than nearby Nowy Targ or Białka Tatrzańska, which are both higher up in elevation. View Videos or join the USDA Plant Hardiness Zone discussion. If the snow cover is reliable, the actual temperature to which the roots are exposed will not be as low as the hardiness zone number would indicate. The USDA rejected the AHS 2003 draft map and created its own map in an interactive computer format, which the American Horticultural Society now uses. Select Page. Suitability Map for the Probable Winter Survival of Ornamental Trees and Shrubs", "United Kingdom Plant Hardiness Zone Map", "Denmark Interactive Plant Hardiness Zone Map", "Map of Albanian plant hardiness zones based on the WorldClim data for the 1950-2000 period", "Climatic hardiness and heat zones of Albania and their use in evaluating the potential of introducing new plant species", "LAS PLANTAS ORNAMENTALES Y SUS ZONAS DE RUSTICIDAD EN ESPAÑA", "Weather and Climate: The Climate of Sarajevo", "Projected changes in cold hardiness zones and suitable overwinter ranges of perennial crops over the United States", Hardiness Zone maps for several continents, Interactive USDA Plant Hardiness Zone Map, Plant Hardiness Zones of Canada – Interactive Map, https://en.wikipedia.org/w/index.php?title=Hardiness_zone&oldid=1010499505, Short description is different from Wikidata, Articles with unsourced statements from July 2016, Articles with unsourced statements from August 2019, Articles with unsourced statements from January 2021, Articles needing additional references from September 2020, All articles needing additional references, Wikipedia external links cleanup from October 2012, Creative Commons Attribution-ShareAlike License, X₁ = monthly mean of the daily minimum temperatures (°C) of the coldest month, X₂ = mean frost free period above 0 °C in days, X₃ = amount of rainfall (R) from June to November, inclusive, in terms of R/(R+a) where a=25.4 if R is in millimeters and a=1 if R is in inches, X₄ = monthly mean of the daily maximum temperatures (°C) of the warmest month, X₅ = winter factor expressed in terms of (0 °C – X₁)Rjan where Rjan represents the rainfall in January expressed in mm, X₆ = mean maximum snow depth in terms of S/(S+a) where a=25.4 if S is in millimeters and a=1 if S is in inches. It revised hardiness zones, reflecting generally warmer recent temperatures in many parts of the country, and appeared similar to the AHS 2003 draft. These maps are based on the average annual extreme minimum temperatures.