USDA Zone 1A

Average annual minimum temperature: -51°C to -48°C (-60°F to -55°F)

This is one of the coldest USDA hardiness zones, typical of interior Alaska, northern Canada, and high-altitude regions. Winters are severe enough that most ornamental and vegetable gardening happens in a short, intense summer season. Perennials need to be exceptionally cold-hardy, and many popular garden plants can only be grown as annuals or overwintered indoors.