don't waste your time trying to straighten it, if possible you can cut it into smaller usable areas, but you need to buy a new mat. they are never the same after that happens and even the manufacturer will tell you this pretty much makes the mat unusable...i've had this happen so many times, mat in hot car...mat in storage, it is a real bummer but sometimes you can cut a couple usable pieces.it is very dangerous to try to cut on it though, the warp can cause the cutter to 'jump/skip' and those blades cut fast and deep.