Although conditions are generally desertlike, three climatic regions can be distinguished. Southern Mauritania has a Sahelian climate; there is one rainy season from July to October. Annual rainfall averages 66 cm (26 in) in the far south; at Nouakchott the annual average is 14 cm (5.5 in).
Trade winds moderate the temperature in the coastal region, which is arid. The average maximum temperature at Nouadhibou for January is 26° C (79° F ), and for October 32° C (90° F ); average minimums are 13° C (55° F ) for January and 19° C (66° F ) for July.
Most of Mauritania north of Atar—about two-thirds of the country—has a Saharan climate. Daytime temperatures exceed 38° C (100° F ) in most areas for over 6 months of the year, but the nights are cool. Average annual rainfall at Atar is 10 cm (4 in).