With the exception of the province of Asir on the western coast, Saudi Arabia has a desert climate characterized by extreme heat during the day, an abrupt drop in temperature at night, and very low annual rainfall. Because of the influence of a subtropical high-pressure system, there is considerable variation in temperature and humidity. The two main differences in the climate of Saudi-Arabia can be felt between the coastal areas and the interior.
The average summer temperature is about 45° C, but readings of up to 54° C are not unusual. The heat becomes intense shortly after sunrise and lasts until sunset, followed by surprisingly cool nights. In the winter, the temperature seldom drops below 0° C, but the almost total absence of humidity and the high wind-chill factor make a quite cold atmosphere. In the spring and autumn the heat is temperated, temperatures average around 29° C.
The region of Asir along the Western coast is influenced by the Indian Ocean monsoons, usually occurring between October and March. An average of 300 millimeters of rainfall occurs during this period, that is about 60 percent of the annual precipitation. For the rest of the country, rainfall is very low and erratic. The entire year's rainfall may consist of one or two local, heavy cloudbursts or Thunderstorms.