When you're trying to decide if a certain plant will grow in your garden, you often begin by thinking about your typical winter and summer temperatures. Will the plant freeze in January? Will it bake and shrivel come August? But while summer heat and winter cold are crucial considerations, other climatic features are just as important. Do you garden in a humid region or in one that's very dry? Is your weather windy all the time, or is it typically calm? Perhaps you're living in a sunny area where rain is the exception; perhaps you garden in frequently overcast conditions where rain comes year-round. All these factors play a role in determining the success or failure of the plants you want to grow.
Latitude, elevation, and jet streams are the three general factors determining climate. Several other factors play a role, as well: amount of wind, timing and amount of annual rainfall, location of mountain ranges (which, in turn, has some influence on the preceding two factors), and the proximity of large bodies of water.
The farther north of the equator a place is, the colder its winters are likely to be, and the longer the wintry weather is likely to last. Winter may arrive early, too--as shown in the photo at right.
The higher your elevation, the cooler the temperatures will be, in both winter and summer. The growing season is usually shorter, as well.
The strong, fast high-altitude air currents known as jet streams affect climate by picking up air of all types--moist, dry, warm, cold--and carrying it to other areas. The jet streams tend to dip farther south in winter and move more to the north in summer, following the movement of the sun. The predictable storms that follow the jet streams' path are largely responsible for the rainy and dry seasons we experience.
Windy or calm conditions
Some areas are perpetually windy; in others, windy weather is associated only with certain seasons. Wind dries out plants and soil, and it's hard on plants with delicate foliage and flowers. You may be able to compensate by providing windbreaks and extra water, and by choosing plants that withstand wind successfully.
Timing and amount of rainfall
Many plants are accustomed to receiving a certain amount of rain at a particular time of year, depending on the conditions prevailing in their native regions. In general, the eastern half of the United States has rainy summers, while summers in the West are dry (though early summer can be wet in the Pacific Northwest). Many plants native to the East require extra summer water if planted in the West; conversely, some western natives will die in eastern gardens, drowning in the summer rain. Be sure the rainfall where you live suits the plants you choose.
Location of mountain ranges
Mountains interfere with basic wind patterns and the movement of air masses: depending on their height and alignment, they either block the wind's progress or direct it. They also cause moist air to rise and cool, so that more rain is deposited on one side of a mountain than on the other. If you live near hills or mountains, your climate may differ from that of a neighbor living on the opposite slope: you may live on the west side of a mountain and receive 40 inches of rain per year, for example, while someone on the eastern side, just 20 miles away, gets only 12 inches.
Influence of water
If you live near the ocean or a large inland body of water, your climate will differ from the climate at the same latitude some miles inland. In Buffalo, New York, for example, the nearby Great Lakes produce extremely snowy winters. In San Francisco, California, the Pacific Ocean makes for cool, overcast summers. You'll need to account for these conditions in choosing plants for such ocean or lakeside regions.Summer Heat and Winter Cold
Even if you're careful to choose plants well adapted to your climate, there are times when they may require protection from heat, cold, or wind. Seedlings and newly set-out transplants, for example, are vulnerable to both heat and cold. In mild-winter areas, tropical and subtropical plants (such as citrus trees) may need occasional protection from frost; where winters are very cold, certain shrubs and young trees may need protection all winter long. And some shade-loving plants must have sun protection and high humidity throughout the growing season.