During the summer, which lasts roughly from May to October, the air generally is dry, but southeasterly winds often raise daytime humidity to 90% for a few weeks in August or September. Between November and April, the climate is pleasant, with cool nights and warm sunny days. In December and January, night temperatures occasionally touch the freezing point. Summer temperatures range from 29° C (84° F ) in the morning to more than 49° C (120° F ) in the shade at noon. Frost, almost unknown on the coast, is common in the interior. Annual rainfall, which averages less than 25 cm (10 in), comes in the form of showers or storms between October and April. Cloudbursts have amounted to as much as 6.4 cm (2.5 in) of rain in one day, and can heavily damage roads and houses. The prevailing northwest wind (shamal) is a cooling breeze in summer.