Almost every gardening article online was written for the United States. The trap: an American “Zone 5” and a Canadian Zone 5 do not mean the same thing. Pick your city to see your real numbers.
No. The USDA system is based on winter minimum temperature alone. Natural Resources Canada’s system factors in seven variables — winter minimum, summer maximum, frost-free period, rainfall, snow cover and wind. So a Canadian “Zone 6” is defined differently from a USDA “Zone 6” even though the number looks identical. We deliberately do not convert one into the other: NRCan already publishes a separate USDA-method map of Canada for cross-border comparison.
Unit converter
°F→— inches→—
Sources: zones — Natural Resources Canada Plant Hardiness Zone Map (planthardiness.gc.ca); frost dates — Environment and Climate Change Canada climate normals.
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