POLAR AND TUNDRA
Polar climates are cold and dry, with long, dark winters. In the tundra (a treeless region bordering the Arctic), temperatures rise above freezing for only a few months each year.
Boreal (cold coniferous) forests lie south of the tundra, stretching across much of northern Canada, Scandinavia, and Russia. Temperatures fall below freezing for 4–6 months a year.
On mountains, the temperature decreases with altitude (height), and many high peaks are always covered in snow. Mountain climates are usually wetter and windier than lowland regions.
Temperate climates have warm summers and cool winters with year-round rain or snow. Temperate forests are characterized by deciduous trees, which lose their leaves during the winter.
A Mediterranean climate is found in regions bordering the Mediterranean Sea, and in Australia and California. It is characterized by hot, dry summers and cool, wet winters.
Earth’s deserts are hot and dry year-round, and usually receive less than 10 in (250 mm) of rainfall a year. Deserts are often found in the center of continents, far from the sea.
Dry grasslands are found in the center of continents where temperate variations are extreme. They have hot summers, cold winters, and little rainfall, so very few trees can grow there.
Tropical grasslands, such as the African savanna, lie between desert areas and tropical rainforests. The climate is hot all year, but with a distinct wet season and dry season.