Its pretty hot here where I live during the summer as well(though I do have AC at home), and one thing that I've done is I have a winter OC, and a summer OC. During the winter when the ambient temps go down a bit I have a preset for a higher overclock, and when the Ambient temps go up during the summer, I switch to the preset with the lower overclock. You can definitely still OC your CPU, you'll just have to watch your temps pretty carefully. I would get a solid heatsink, and then I'd just keep a temperature monitoring software (like coretemp or realtemp) running all the time and make sure you're not getting too hot.
you can also generally set a shut-down temperature (say 70-80C or so) and your comp will automatically shut itself down if the CPU hits that temperature. You can also set alarms with things like Coretemp that will alert you if your CPU hits whatever temperature.