Looking at your picture, I notice a complete lack of an exhaust fan at the back. I assume that mount location accommodates a 120mm fan. I would start there. If there is a mount location in the front of the case, I would install a fan there as well. The rear fan should be exhaust, the front fan should be an intake fan. At a bare minimum you should have two fans. From the information I'm seeing on that case, it has 5 mount locations, but no fans actually come with the case. Adding an intake and exhaust fan should lower your temps fairly significantly even with your high ambient temperatures.
If you want to improve your CPU temps, it would also help to use a HSF (Heatsink Fan) that is better than stock. Depending on availability the Hyper 212 EVO is an excellent cooler for the money. If you go this route, just make sure that your case is wide enough to accommodate a tall cooler. The Hyper 212 EVO is 159mm tall. Most cases now list a maximum cooler height in there specs.
Edit: Well I looked for information on what is the max cooler height that case will accommodate, but there isn't any. The other option if this is something you'd like to explore is to measure from the bottom of the stock heatsink up to where the side panel would be. Take that measurement and subtract about 5mm to take into account the side panel and whatever the result is, that's your maximum cooler height.