Plant Hardiness Zones for other

For other regions in the world you need know your annual minimum temperature over a number of years (say 10years) so you can match to USDA Chart and share our plant data across the world. The statistic used by the USDA is the average annual minimum temperature. This causes some confusion straight away, because in Australia the term average annual minimum temperature is used to mean the average minimum temperature over the whole year, whereas the USDA means the average, over ten or more years, of the very lowest temperature (the absolute minimum) observed for each year for each meteorological station. Thus the USDA term - average annual minimum temperature should preferably be called ‘the average annual lowest temperature’.

  The figure given above tends to make places look very cold! For example, Florida, which we think of as a warm place, is in the US Zone 10 which has minimum temperatures from 30°F to 40°F (-1°C to +4°C). Zone 1 (e.g. central Alaska ) is below -50°F (-45°C) which is very cold!