If you are the type who enjoys the sun, Bahrain is the place for you.
There's a popular belief that Bahrain has two kinds of climate - Hot and Hotter. Actually, that's not quite true, as temperatures can drop to the low teens in the winter. If that's when you plan to travel, better bring those woollies!
The peak of summer though can be very hot outdoors, and even sun-worshippers ought to take care when outside.
This is precisely the reason air conditioning is considered something of a necessity rather than a luxury in Bahrain.
Unless you are travelling in winter, light clothing and sunglasses are advisable.
Here's a listing of average monthly temperatures, with rain and humidity.