Salalah gets the tail end of the monsoon distribution over the summer known as the Khareef. The cool-ish weather and rain make it a holiday destination during those days for many Gulf residents keen to experience mini-Manchester in the tropics. Wadis and other drainage systems aren't great at coping with heavy rain, so if that happens, there is short-term flooding which can be intense (Salalah is on a plain situated at the foot of a montain range). There is also the risk of cyclones, though these are rare events. A guard damn is being constructed to protect Salalah - it may well have been completed.

It can rain in Oman (not just Dhofar) at other times of the year, with thunderstorms over the mountains causing flash-floods in wadis (dried-up river beds). But it's not common, and little or no danger if you are sensible.

A cyclone hit Muscat in 2007, causing an enormous amount of damage through flooding and wind. That was a freak event, not one you could plan for.