The AU system:
deepgreenpermaculture.com/2023/08/29/which-usda-hardiness-zones-correspond-to-the-australian-climate-zones/The concept of USDA Hardiness Zones has several limitations we need to be aware of. Since this model is based on the coldest temperatures experienced, it doesn’t incorporate heat levels during summer when determining the zone rating. This means that two regions with the same minimum winter temperatures but with different summer temperature would be assigned to the same hardiness zone.
The Australian climate zones take into account various factors such as temperature, rainfall, humidity, elevation, and specific regional conditions, so they don’t have a direct one-to-one correspondence with the USDA Hardiness Zones.
We can however roughly align the USDA Hardiness Zones with the Australian climatic zones as detailed below:
Tropical Zone:
USDA Zones: Generally, USDA Zones 10-11
Explanation: The tropical zone corresponds to areas with consistently warm temperatures year-round. In the USDA system, Zones 10 and 11 cover regions with relatively mild winters and high temperatures, which can be similar to tropical conditions.
Subtropical Zone:
USDA Zones: USDA Zones 9-10
Rationale: The subtropical zone has warm to hot summers and mild winters. USDA Zones 9 and 10 include areas with relatively mild winters and are thus similar to subtropical climates.
Temperate Zone:
USDA Zones: USDA Zones 4-8
Rationale: The temperate zone encompasses a range of climates with distinct seasons. USDA Zones 4-8 cover a variety of climates with cold to mild winters and warm to hot summers, which can align with temperate conditions.
Arid Zone:
USDA Zones: USDA Zones 8-11 (for regions with desert-like conditions)
Rationale: The arid zone corresponds to dry and desert-like climates. USDA Zones 8-11 can include areas with low rainfall and high temperatures, which are characteristic of arid regions.
Cool/Alpine Zone:
USDA Zones: USDA Zones 1-6 (higher elevations)
Rationale: The cool/alpine zone corresponds to areas with colder temperatures, often found at higher elevations. USDA Zones 1-6 include regions with cold winters and shorter growing seasons, which align with cool and alpine conditions.
We need to keep in mind that while these general correlations provide a rough approximation of USDA zones with Australian climate zones, they aren’t precise matches, so it’s best to check the growing requirements of any plants and their suitability to your location before planting.
