Oman is not a summer destination: temperatures can rise significantly above 40C and humidity is unpleasantly high. However for the rest of the year, from October through to April, it is a wonderfully pleasant place to visit: temperatures will be somewhere in the twenties, perhaps into the thirties in the autumn and late spring.
Rain is fleeting and tends only to come in the middle of the winter as short, sharp showers.
Temperatures are considerably cooler in the mountains than on the coast. Salalah has a very different climate in that it has a monsoon season, called the khareef.
From June to September, wet winds create a thick fog that coats the mountains. Rather than heavy rain, the fog deposits moisture on the vegetation and ground creating luxuriant green hills.