Climate zones

To help you find an author who lives and gardens in the same type of climate as you, GardenDrum uses both Australian climate zone descriptions and the USDA Zone system. In colder climates where low winter temperatures are the most important factor for limiting plant growth, the USDA Zones are the most useful. However, in countries with generally milder climates, like most of mainland Australia, the most important limiter of plant growth is more likely to be maximum summer temperatures or seasonal humidity, so the Australian climate descriptors reflect that.

CST-WT   = Cool subtropical to warm temperate, or USDA Zone 9b-10a

Describes the coastal plains of Australia’s east coast from south of Sydney to the mid north coast, which have mild winters and warm to very warm summers with high humidity. Light to moderate winter frosts are possible in elevated districts and away from the coast. Rainfall is relatively high (800-1200mm or 31-47in), often as storm-event rain in summer and autumn, and with a drier period through spring.

Similar areas are South Africa’s south coast around Mossel Bay, and USA  northern Florida and eastern Texas.

 

CST-T = Cool sub-tropical to temperate, or USDA Zone 10b

Describes the coastal area around Auckland in the north of the North Island of New Zealand, which has warm, humid summers and mild, wet winters, without significant frost. Annual rainfall is 1100-1300mm.

 

WST   = Warm subtropical, or USDA Zones 10b-11a

Describes the coastal areas of Australia’s east coast from the mid north coast to Rockhampton, with its very warm, humid and wet summers and dry, mild to warm winters. Average rainfall is 800-1200mm (31-47in) and most areas are frost-free.

Similar areas are South Africa’s east coast from east London through Durban, and USA central Florida and south-east Texas.

 

T   = Tropical, or USDA Zone 11b-13a

Describes the area in Australia north of the Tropic of Capricorn, including Cairns, Darwin and Broome. Summers are very warm to hot and winters above 15 degrees C (60 degrees F). A summer monsoon season brings high rainfall (often over 2000mm or 78 in in the north and east but drier in the west). Damaging tropical cyclones are common. Humidity builds from late spring and continues through until late autumn/fall.

Similar areas are southern Florida and Hawaii.

 

M   = Mediterranean, or USDA Zone 9b-10a

Describes the areas of southern and south-western Australia, including Adelaide and Perth and inland Victoria and NSW. Summers are very warm to hot with low humidity and rainfall, as well as regular droughts. Rainfall is mainly in winter and around 400-600mm (16-23in), with up to 1000mm (40in) in some districts. Heavy winter frosts in elevated and inland areas, and cooler summers in elevated districts.

Similar to southern Europe, and USA California and South Africa’s west coast around Cape Town.

 

T   = Temperate, or USDA Zone 9b

Describes the areas of southern Australia, including Melbourne, and elevated areas in NSW and southern Queensland. Summers are warm and winters cold to cool. Rainfall of around 600-800mm (23-31in) is spread throughout the year but with a spring peak. Severe frosts inland.

 

CT   = Cool temperate, or USDA Zone 9a

Describes the mountainous districts of NSW and Victoria, including Canberra, as well as Tasmania. Summers are warm to very warm but with low humidity, and winters are cold with most nights below 0 degrees C (32 degrees F). Frosts are common from autumn to spring, and snow often falls on the peaks and higher areas.

Similar areas include UK’s London, southern and western coast, Ireland’s west coast. In South Africa, the highveld region around Johannesburg experiences similar temperatures but is semi-arid.

 

USDA Zone 8b

Describes the hardiness zone of coastal western Scotland, southern England, western inland Ireland and inland eastern and southern USA, with average annual extreme winter temperatures down to minus 9 degrees C (15 degrees F)

 

USDA Zone 7a

Describes the hardiness zone of northern Virginia and Washington DC, with winter extreme minima down to minus 17 degrees C (0 degrees F)

 

USDA Zone 6b

Describes hardiness zone of USA Boston Massachusetts, and central USA, with winter extreme temperatures down to minus 20 degrees C (minus 5 degrees F)