Climates of North America

Today it is also very wet and very dry. North America while another is warm. One region is usually mild and while another is mostly hot and dry. This pattern of miss freezing temperatures and snow. Climate is also partly controlled by great air masses far to the south. As this warm tropical air advances northward, it brings summer warmth to much of the continent. It also brings rain, especially in the east. The cold air usually stays far to the north in summer, but blankets most of the land in winter. When the cold air retreats again, it continues to keep one northern area near freezing even in summer. In winter, although the cold air affects most of the continent, it does not reach the southern tip of Florida, which remains warm all winter. It is almost as warm here in mid January as it is in July. Frosts are very rare. Summer never really ends and farms can produce crops all year round. Tropical plants and animals also flourish in this warm wet climate. The tip of Florida has a tropical climate. Thousands of miles to the north is a region of perpetual ice and snow. Winter never ends on the mile thick Greenland ice cap. During the long Arctic night, the ice cap and the frozen Arctic Ocean act as a refrigerator, cooling much of the continent. The Greenland ice cap is said to have an ice cap climate and is virtually lifeless. This region is not permanently covered by ice and snow, and there is life here. As the long Arctic night slowly ends, some of the sea ice melts and summer activities begin. For a short time each year, the ice and snow disappear on this great Arctic plane or tundra, and the surface of the earth thaws just deeply enough to allow very small, hardy plants to grow. The Arctic tundra is said to have a tundra climate. Here, the summers are only slightly longer, but this region has a very different appearance. On the southern edge of the treeless Arctic tundra, one comes to the tree line. It marks the limit of the great evergreen forest that covers much. People come here for wood or minerals or to hunt and fish. They raise few crops even where cultivation is possible. Because summers are usually cool and very short, followed by long, bitterly cold winters. This forested region has a subarctic climate. To the south is an area where the climate is not so severe. Longer summers with plenty of rain are ideal for growing corn, the most important single crop in North America. The corn provides abundant fodder for beef and dairy cattle and other livestock that help to feed the many great cities which have sprung up in the region. Although summer is often hot and sticky, it is quickly followed by cold air and snow that sweeps rapidly over the continent and remains for over a third of the year in parts of this region. This area has a humid continental climate. The northern part has shorter summers and colder winters. The southern section has longer summers and milder winters. To the south is a region with a climate more like that of tropical Florida. Cotton needs about 6 months of warmth and plenty of moisture to brighten and it grows well here in the long hot summers. The air is usually very humid and there is much rain and even during the short winter clouds bring rain much more often than snow. This region has a subtropical climate. Now this north to south pattern of climates is complete. In the far north there is a region that has no warm period. The further south a region is, the longer and warmer are its summers. Mostens get an adequate supply of moisture. All these climates are determined mainly by differences in temperature. But the climates of the west are determined mainly by rainfall or the lack of it. For instance, this whole region is usually very dry because the winds that bring rain to the east usually do not reach it and the winds from the Pacific lose most of their moisture at the western mountains. Dryness is far more important than temperature in determining conditions. Here it is too dry for trees to grow on these vast grasslands which are sometimes called steps. Cattle graze where the land is hilly or too dry to cultivate. And hard wheat for making bread is an important crop on the prairies where there is a little more moisture. This grasslands region is said to have a step climate on the west coast. Also, it is mainly the amount of moisture that controls climate. In summer, there is some rain along the coast. But in winter, the winds move south and bring heavy rainfall to one area, less to another. Further south, there is little or no rain at all. This region receives the most rainfall in North America. evergreens like the Douglas fur grow to immense size in this very wet and mild Pacific climate. In winter, the mild Pacific winds bring a great many dull, rainy days to the coastal valleys. There is little frost or snow. The coastal area with the heavy rainfall has a marine climate. This coastal area receives almost no rain at all. Although the land is warm and on the edge of the ocean, the winds are dry and bring no rain from the sea. And for many miles along the coast of lower California, there is barren white sand. In this desert climate, there is almost no life. By drilling wells and building irrigation canals from distant rivers, man can change the desert and grow many useful crops. Between the very wet and very dry regions is the area that gets a little rain each year. Oranges, lemons, figs, and other crops are grown in the irrigated orchards of Southern California. This region has the very warm, dry summers and mild winters with little rain that are typical of many Mediterranean lands. And this dry, warm climate has attracted millions of people to this small area. Winters are so mild that on New Year's Day, the famous Roseb game is usually played in pleasantly warm weather. This warm region with its winter rainfall has what is called a Mediterranean climate. The land surrounded by mountains is shut off from almost all rain. Only very hardy domestic animals like sheep and goats can survive where water is so scarce. Many plants are adapted to life in severe desert conditions and so are some animals. From the desert, one can see mountains that have captured some moisture from the air. Partway up the mountains, there may be forests, and on the cold peaks, tundralike vegetation grows. The melting snow provides moisture the year round for many birds and animals. There is no one mountain climate. There are many different climates which change according to altitude. Much of the arid land between the mountains has a desert climate. The western climates differ mainly in the amount of rainfall they receive. The marine climate gets abundant rainfall while the desert climate gets almost none. In the west, wet and dry are the two extremes that most affect climate. The extremes elsewhere in North America are hot and cold. On the Greenland ice cap, it is always cold. And in tropical Florida, it is almost always warm. North America also has many climates between the extremes of hot and cold, wet and dry. In fact, there are examples here of most of the climates found throughout the world. [Music]