Under the influence of the monsoons, in the summer Iraq has a constant northwesterly wind (shamal), while in winter a strong southeasterly air current (sharqi) develops. The intensely hot and dry summers last from May to October, often reaching 49°C (120°F). Winters, lasting from December to March, are damp and comparatively cold, with temperatures averaging about 10°C (50°F).
Occasional heavy snow in the mountains along the Iranian and Turkish borders can cause extensive flooding in central and southern Iraq during the spring melt. Spring and autumn are brief transition periods. Normally, no rain falls from the end of May to the end of September. With annual rainfall of less than 38 cm (15 in), agriculture is dependent on irrigation.