What is Climate?

            No matter where you live, your climate has a great deal to do with the plant and animal life that is present. Your climate also has a great deal to do with the activities of people. Climates are different from place to place.
            Weather and climate. Weather is the sum of all the conditions of the air that may affect the earth's surface and its living things. To that definition might be added "at a given time" or "on a given day." Climate is the average of all the weather conditions in a certain place over many years. The climate in a certain place does not change very much from year to year, even though the weather may change a great deal from season to season. So when people talk about climate, they are not talking about the weather on a certain day or in a certain season. Rather, they are talking about the kinds of weather they can expect during the course of many years. Keep in mind, however, that there may be extreme conditions of weather that occur in a certain place. Extreme conditions of temperature might occur within the climate of a northern city.
            Climate and plant life. The kinds of plants in one climate might be very different from the kinds in another. In a climate that is very cold and windy much of the year, many of the plants are small and have small leaves. Such plants may produce flowers only every other year because the growing season is short.
            Climate and animal life. Certain animals are well suited to live in a desert climate. These animals conserve water in their body and seek shelter during the hottest part of the day. In a very cold climate the warm-blooded animals grow a great deal of hair or fur before the winter season begins. Some of them also migrate during the winter. Animals like caribou migrate across frozen, snow-covered lakes in the winter.
            Climate and people's activities. The kinds of work people do and the other kinds of activities they do depend a great deal on the climate where they live. People cannot grow oranges in most states because the freezing weather in the winter might kill the trees. Many people spend a great deal of time outdoors in the summer. But people that live in desert areas may spend a great deal of time indoors during the summer.

How Climates Are Different

            What determines the climate? There are many things that help determine the climate of a certain place. One of these things is the prevailing wind. Mountain ranges and hills, large bodies of water, ocean currents, the place's distance from the equator, and its height above sea level also help determine the climate. Mountains and hills cause air masses that move toward them to rise. As an air mass rises and cools, water vapor condenses and falls to the earth. If the prevailing wind comes from the west, the rain will fall on the west side of the mountains. This side of the mountains will get enough moisture so that crops may be grown. On the east side of the mountains, however, the climate will be dry. Large bodies of water affect the climate, too. Large bodies of water have a moderating effect on the temperature. That is, if it is cold inland, the land near a large body of water will not be as cold as it is inland. If it is hot inland, the land near the water will not be as hot. So the climate is usually milder near the water. Inland, however, there may be great differences between the coldest and warmest temperatures. Ocean currents play an important part in determining the climate, too. There is a current called the Gulf Stream. This current moves from the warm Caribbean area, along the east coast of the U.S., to about Cape Hatteras. Then most of it moves across the Atlantic Ocean to Europe. Northern Europe would have a colder climate than it has if this warm current did not reach its coasts. The distance from the equator, or latitude, probably has more to do with the climate at a certain place than anything else. The farther you go from the equator, the lower the average yearly temperature will be. Also, the farther you go from the equator, the larger the yearly temperature range (from warmest to coldest) will be. The height above sea level of a place also helps determine the climate. The higher you go above sea level, the lower the average yearly temperature will be. You may know that there is snow all year long on the tops of many high mountains, even at the equator.
            Climates of the world. There are 3 major groups of climates in the world. These are (1) the tropical climates, (2) the middle-latitude climates, and (3) the polar climates. Some people would name a fourth group – the highland climates. There are further divisions of each of these major groups. In tropical climates, the average temperature for any month does not go below 18°C (64°F). These climates are close to the equator. In middle-latitude climates, the average for the coldest month must be below 18°C (64°F). But the average for the warmest month must be at least 10°C (50°F). In polar climates, the average for the warmest month is below 10°C (50°F). But highland climates are cold, too. Highland climates are found on mountains and high hills. The higher you go above sea level, the colder the temperature will be. Because of this, highland climates may change a great deal the higher up you go. At the top of high mountains, highland climates may be much like polar climates.