Climate

1. Rainfall

Saudi Arabia is an area of dry, stable, subsiding air which gives rise to hot, dry and near cloudless skies with dry days most of the year. Occasionally disturbed tropical monsoon weather may reach the Kingdom, bringing rain to the south of the country in the summer. In winter, remnants of the mid-latitude low pressure system may penetrate the north of the country giving rise to most rain in the region.
Precipitation due to high altitude and proximity to the Red Sea augments rainfall along the south-western escarpment. Daytime on-shore sea breezes force the moist air from the Red Sea to ascend, giving rise to afternoon showers and thunderstorms. Annual precipitation in the mountains south of Taif is above 125 mm and may exceed 600 mm.

2. Temperature and Humidity
Temperatures are subject to considerable diurnal and seasonal fluctuations. Winters (December to February) are cool to warm. Summers (June to September) tend to be very hot with temperatures above 40° C widespread and common and may approach 50° C. Humidity is generally low, except along the coasts where it may be quite high.

Average August temperature in Jeddah 32° C but may reach 49° C, winter temperature average 24°C, and relative humidity varies seasonally between 55% and 65%.

Summer months in Riyadh are intensely hot with a daily maximum about 45? C. Winters are cooler, with a maximum temperature of 22° C declining to 10°C or lower. Relative humidity also varies with seasons with typical summer humidity of between 15 to 20 %.

The Gulf coast is warm and humid in summer with average maximum of 42°C and winter maximum average of 22° C. Humidity varies seasonally greatly from 40% in summer to about 70% in winter.