Source: The Library Of Congress Country Studies
With the exception of Dhofar region, which has a light monsoon climate and receives cool winds from the Indian Ocean, the climate of Oman is extremely hot and dry most of the year. Summer begins in mid-April and lasts until October. The highest temperatures are registered in the interior, where readings of more than 50° C in the shade are common. On the Al Batinah plain, summer temperatures seldom exceed 46° C, but, because of the low elevation, the humidity may be as high as 90 percent. The mean summer temperature in Muscat is 33° C, but the gharbi (literally, western), a strong wind that blows from the Rub al Khali, can raise temperatures from the towns on the Gulf of Oman by 6° C to 10° C. Winter temperatures are mild and pleasant, ranging between 15° C and 23° C.
Precipitation on the coasts and on the interior plains ranges from twenty to 100 millimeters a year and falls during mid- and late winter. Rainfall in the mountains, particularly over Al Jabal al Akhdar, is much higher and may reach 700 millimeters. Because the plateau of Al Jabal al Akhdar is porous limestone, rainfall seeps quickly through it, and the vegetation, which might be expected to be more lush, is meager. However, a huge reservoir under the plateau provides springs for low-lying areas. In addition, an enormous wadi channels water to these valleys, making the area agriculturally productive in years of good rainfall. Dhofar, benefiting from a southwest monsoon between June and September, receives heavier rainfall and has constantly running streams, which make the region Oman's most fertile area.
Data as of 1993