I've read some of the replies to your question and couldn't help but interfere. Turkey in general is hot during August ie, 35 - 40 degrees tops. However, there is a pattern, upto 15th August is hot the second half generally going into a rainy season and could even cool down to 25 degrees. It will then start to get warmer mid September (30 - 35 degrees) then autumn starting early October.

Please rest assured, no matter how hot it is you know during the evening it will be pleasant and you will have trees to seek shelter. Hope you have a pleasant trip!! A turk in Qatar.