The British Isles divided into USDA style weather zones
Click on the map for a more detailed view
The original work carried out to gather the Met office records and create the mapping information as it is today was done by Trebrown Nursuries. My thanks to Phil Markey for letting me use that information to create this version of the Hardiness Zone Map!
| Average Annual Minimum Temperature |
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| Fahrenheit | Zone colour code | Centigrade | ||||
| 0 | to | 5 | 7a | -15.0 | to | -17.7 |
| 5 | to | 10 | 7b | -12.3 | to | -14.9 |
| 10 | to | 15 | 8a | -9.5 | to | -12.2 |
| 15 | to | 20 | 8b | -6.7 | to | -9.4 |
| 20 | to | 25 | 9a | -3.9 | to | -6.6 |
| 25 | to | 30 | 9b | -1.2 | to | -3.8 |
| 30 | to | 35 | 10a | 1.7 | to | -1.1 |
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The zones used in this map are based on the system that the United States Department of Agriculture uses. In this zone hardiness map, the British Isles have been colour coded with seven split zones, from 7a to 10a, in order to reflect the average annual minimum temperature experienced. There is nowhere else in the world, at this northerly latitude, that experiences such mild winter temperatures - Quebec, for example, at latitude 46° can experience winter temperatures down to -30° C (-22° F). Our mild winter temperatures are due to the warming effects of the gulf stream. Something that is worth a mention here is the fact that: even though some areas in the UK might expect to receive similar winter temperatures to some parts of Florida, this needs to be weighed up against the reality that winters are longer here. The fact remains that the UK is situated on a much more northerly latitude and so experiences a longer winter - in other words those winter temperatures, favourable though they might be, are more prolonged and the day light hours are less. So, in actual fact, although the temperatures might seem similar, the winter is more demanding on the cold hardiness of a plant. More about UK climate and weather statistics from the Met Office |