The US hardiness zone system, in which the hardiness of a vast range of plants is matched to parts of the country with winters they can tolerate, is well known to gardeners everywhere. The Hardiness Zones Map produced and recently updated by the USDA, shows clearly which parts of the country are in which zone, numbered zone 1 (the coldest) to zone 13 (the warmest), and these ratings correspond to those assigned to just about every plant you could ever think of growing.
But there are also other, less familiar approaches to hardiness. Firstly, there are Canada's Plant Hardiness Zones. Used in the same way as the USDA system, and focused on low winter temperature tolerance, it builds in far more factors than simply lowest winter temperatures. There is also The American Horticultural Society's (AHS) Plant Heat Zone system, which measures tolerance of summer heat.
