Many systems have been developed for classifying climates. The simplest is based on latitude, dividing the world into five zones—the north polar, north temperate, torrid (or tropical), south temperate, and south polar. Because it ignores such factors as altitude and the effect of the oceans, this system is not very accurate. Another system classifies climate as continental (cold winters and warm summers) or marine (mild seasons). A more complete classification is the one devised by Wladimir Kppen (1846-1940), a Russian-German climatologist. He defined five major types of climate:

The average temperature of the coldest month is above 64 F. (18 C.). During the two rainy seasons 6 to 15 inches (150 to 380 mm) of rainfall a month are usual. These climates are found in much of northern South America, central Africa, and Southeast Asia.

There is less than 20 inches (500 mm) of rainfall a year, as in the western plains of North America and deserts throughout the world.

The average temperature of the coldest month is between 64 and 27 F. (18 and -3 C.). Yearly rainfall ranges from 20 to 40 inches (500 to 1,000 mm). These climates prevail in the southeastern United States and western Europe and on the coasts of the Mediterranean Sea and Indian Ocean.

The average temperature of the coldest month is below 27 F. (-3 C.) and the average temperature of the warmest month is above 50 F. (10 C.). The yearly rainfall averages under 20 inches (500 mm). This is the climate of Siberia, Alaska, and northern Canada.

The average temperature of the warmest month is below 50 F. (10 C.). Although precipitation is slight, low temperatures allow what falls to accumulate in permanent snow and ice fields. The polar zones are the Arctic and Antarctic regions. However, polar climates are also found on high mountain peaks, even those near the Equator.