The U.S. state of Hawaii, which covers the Hawaiian Islands, is tropical but it experiences many different climates, depending on altitude and surroundings. The island of Hawaiʻi for example hosts four climate groups on a surface as small as 4,028 square miles (10,430 km2) according to the Köppen climate types: tropical, arid, temperate and polar. When counting also the Köppen sub-categories – notably including the very rare cold-summer mediterranean climate – the island of Hawaiʻi hosts 10 climate zones. The islands receive most rainfall from the trade winds on their north and east flanks as a result of orographic precipitation. Coastal areas are drier, especially the south and west sides or leeward sides.