As they pass a given spot on the earth, the wind direction changes. For example, a low moving eastward across Chicago produces winds that shift from southeast to northwest. Local winds arise only in specific areas on the earth. Local winds that result from the heating of land during summer and the cooling of land during winter are called monsoons. They blow from the ocean during summer and toward the ocean during winter.
Monsoons control the climate in Asia, producing wet summers and dry winters.
A warm, dry, local wind that blows down the side of a mountain is called a chinook in the western United States and a foehn in Europe. Measuring wind Two features of wind, its speed and its direction, are used in describing and forecasting weather. Wind speed is measured with an instrument called an anemometer. Several kinds of anemometers are used today. The most common kind has three or four cups attached to spokes on a rotating shaft.