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Microclimates

In some areas of the country the climatic regions are broad, changing little over hundreds of miles. But in other place, such as area close to large bodies of water or where mountainous terrain prevails, conditions can change within a matter of feet, creating vary distinct microclimates. On the West Cost, for example, moisture-land storms bring plentiful moisture in the winter, though this moisture decreases sharply as the storm moves inland, shedding its water to the west and leaving desert to the east. This may happen within as little as thirty miles. Even within the one rainfall zone, rainfall can vary greatly depending on the impact of hills, or elevation; often, lee sides of promontories are in a mini-rain shadow area whereas higher slopes catch more clouds and moisture. Elevation and exposure can play a role in shaping temperature. We might expect temperatures to increase or decrease as we move south or north over great distances, but even locally, the smallest valley can trap cold air, causing overnight temperatures to be as much as ten degrees colder where, in the same vicinity, a couple of hundred feet of elevation allows cold air to drain away, raising overnight temperatures. There, as well, wind exposure is often greater, keeping air stirred up and preventing the coldest air from reaching ground level. An example of this is the citrus belt, which lies a few hundred feet up in the foothills surrounding California's San Joaquin Valley. Areas adjacent to large bodies of water can also benefit from warmer temperatures. This includes coastal areas, and also areas around the Great Lake, which may be, in some cases, a full zone above neighboring inland area. For gardeners, large areas such as those influenced by the factors above are noted and designated as warmer winter locals on the Zone maps. Though no one map could include all the climatic factors that influence one stop on the planet, the USDA Zone maps included here provide, at the least, the average minimum temperatures experienced throughout these broad-ranging climates. However, with so many local influences on weather, especially temperature, it is still wise to become familiar with you own microclimates. The first step is often as simple as observing what is growing well-or not so well- in the neighbor's garden.