Microclimates prevail throughout this mountainous region, with rainy winters in coastal zones and winter dryness in the eastern deserts. Mountain areas experience winter snow pack and freezes. Alaska winters are the most severe of all.

Mainland microclimates are numerous, ranging from high and low deserts to the maritime Mediterranean climate of coastal areas. The winter rainy season brings cool temperatures. Freezes are infrequent. In Hawaii, mild winter temperatures prevail.

The Rocky Mountains and Sierra Nevada Mountain Range are the two biggest influences on the weather. Winter snow is predictable for much of the region. The summer gardening season is short, with cool nights; frosts can occur at any time.

This region feels the impact of Arctic air from Canada. Winter frequently brings episodes of freeze and thaw and harsh drying winds. Areas near the Great Lakes feel the "lake effect" in cooler, late-breaking summers and milder winters. The last frost date can occur anytime from mid- to late May.

The Lower Midwest, where the South meets the North, encompasses many microclimates. These zones feel the humid influence of Gulf air streams in early summer and often suffer icy blasts of Arctic air in the winter. The growing season may stretch year-round in the southernmost parts of the region.

Northeastern gardens weather long, extremely cold winters. In the coldest zones, the ground freezes to a depth of several feet. Summers are short, cool and sometimes rainy.

Severe, cold winters characterize most of the region, with freezing occurring in all but the most temperate coastal and bay zones along the southern East Coast.

Hot, humid summers give way to generally mild winters. But Arctic air can bring occasional winter ice storms and frigid temperatures to Arkansas, Georgia and the Carolinas. The region's last frost date usually falls before late March.