In previous years, I've just built up a 30 or 40 gal summer stockpile of beers, with ones that can age being used last, and then not brewing at all the hot weather. I've got a basement now though, and its about 15 degrees C right now, so I expect to be able to brew well into summer with no issues.
I might get a fermentation freezer next year if the esters are out of control this season though.
I've also used the swamp cooler method mentioned above, it works ok, but not ideal.
You could get a window air conditioner too