The rugged mountain ranges and the Atlantic Ocean moderate the tropical heat of Morocco. Temperatures in Casablanca range from an average minimum of 7°C (45°F) to a maximum of 17°C (63°F) in January and from a minimum of 18°C (64°F) to a maximum of 26°C (79°F) in July. Temperature variations are relatively small along the Atlantic coast, while the interior is characterized by extreme variations. The eastern slopes of the Atlas Mountains, which divert the moisture-laden Atlantic winds, have a rigorous pre-Saharan climate, while the western slopes are relatively cool and well watered. The rainy seasons are from October to November and from April to May. Maximum annual rainfall (75–100 cm/30–40 in) occurs in the northwest. Other parts of the country receive much less; half of all arable land receives no more than 35 cm (14 in) a year.