I am based here in Oman.
Where are you coming from? What activities you want to do?
April-August is not the best time to come here for tourism. The weather is so hot because it is summer time here. Expect a temperature of more than 30deg day and night time. There are a lot of place to see like museums, forts, castles, and beach. You don't need to take a plane ride to experience a good beach unless you really want to visit Salalah which is also a tourist destination here.