It’s a well-known fact, that the geographical position very often influences the climate and weather of any country. The United States is no exception. Here, the Cascade Mountains and the Sierra Nevada Mountains, due to their being close to the west coast, catch the largest share of the rain off the Pacific Ocean. As a result there is too little rain for almost the whole western half of the Unites States, which lies in the "rain shadow" of the mountains. In a great part of that territory farmers must depend on irrigation water from the snows or rains.
One of the most important geographic boundaries in the United States is the 50-centimeter rainfall line. It runs north and south almost through the middle of the country. East of the line, farming here is easy and the population is relatively large. West of the line, you can find man-made irrigation systems, dry-farming and grazing. There are fewer people living here. West of the RockyMountains, there are vast areas without any trees. In this part of the country are the deserts which receive as little as over 12 centimeters of rainfall a year.
If there were no mountains or oceans, then the amount of the heat would progress from north to south. Instead, there are all kinds of unexpected differences in climate. For example, all along the western coast, the temperature changes little between summer and winter. The climate along the northern part of this coast is similar to that of England.
But in the north central part of the country, summer and winter are very different. There the average difference between July and January is 36 degrees centigrade (°C). The coldest days of a typical January day may be — 40 degrees °C, and the hottest July day may be +45 degrees °C. In the eastern part of the United States, the difference between summer and winter is also distinct, but not so extreme. Near the southwestern corner of the country, the climate is mild and spring like in winter.
The variations in temperature within the United States have had a marked effect on the country’s economy and living standards. There is a long crop-growing season along the south-east coast where cotton is a principal product. In some of the cooler climates or in climates which combine coolness and humidity, people grow apples, wheat and corn. This gives the United States a large variety of agricultural products.
the largest share of the rain — наибольшее количество осадков
the"rain shadow"— «тень от дождя», т. е. в данной местности очень редко идут дожди
a geographic boundary— географическая граница, предел
man-made irrigation systems — построенные человеком (самодельные)оросительные системы
unexpected differences— неожиданные различия
coolness and humidity — прохлада и влажность
wheat and corn — пшеница и кукуруза