As for cold temps - just like Alex TC said, "Cold weather+pressure=warp" - which means you dont really have to worry about cold weather IF, AND ONLY IF you have you records properly stored (ie kept flat, straight, yadda, yadda). As far as protecting from heat your storage needs to be more stringent - as heat will warp your vinyl WAY more than cold. This means that they have to be held more tightly in proper postion, i.e. more pressure keeping them flat. I dont know at what temp vinyl starts to warp, but if you are dealing with heat all you need to do is make sure your records are flat and there is a lot of weight keeping them that way. Also, when vinyl changes temperature quickly it warps A LOT - even if it was't all that hot. So if your records do get hot in the car (but of course you kept them flat ) be sure you keep that pressure on them as they cool. Hope I didnt elaborate too much.
more n o i s e please!