When it's this hot out, you want to make sure you're doing everything you can to stay cool (and keep swampy perspiration at bay). The trick is getting clothes that won't stick to you after you sweat. And while high quality Egyptian cottons are breathable, they're also pricey and well, a little old fashioned. Uniqlo's Airism technology made its debut last year, and we can't get enough of the synthetic fabric. Our favorite way to wear it? We're suckers for their boxer briefs. Cut slim in the thigh, there's plenty of room where it counts, and the ultra breathable fabric regulates heat well and wicks away moisture—not to mention neutralizes odors. They're also available in plenty of timely patterns like polka dot and checkerboard. Or you can simply stock up on the subtle solids. And with their comfortably smooth fit, you can easily slip them underneath slim jeans, lightweight chinos and shorts with ease.