Corn even requires warm nights to mature properly. Soil warmth is also influenced by the number of degree days above freezing. For annual plants, the main remaining climate requirements are enough sunshine and sufficient water. If the plants are watered artificially, most will do best with as much clear, sunny weather as possible. This is one of the reasons variety selection is so important in Alaska.
Perennial plants have additional climatic needs.
To start with, they need a cooling-down period before the first frost in the fall, so they can go dormant properly. Many are also programmed to start dormancy when the days shorten by a specific amount, and this is often later than is needed in many areas of Alaska. Nursery catalogs generally delimit hardiness zones by the lowest temperature expected in an average winter. Of course it makes a difference whether the plant dies down to the roots in winter so that it is affected only by the soil temperature, is a small shrub covered by snow, or has its branches exposed to the winter air. There are other factors affecting perennial survival.