My car usually sits at 850-900 rpm's at idle.. .but yesterday, in the cold weather, I drove it pretty hard, and at a stoplight, the rpm's at idle hovered around 1000-1100... now i think it's back in the mid 900's...

is there something wrong? Or just the cold weather?

mines usually at 750

both those are fine, depending on mods etc. your rpm's will vary.mine sits around 8-900 but like you said if i drive it hard it might go to 1000-1100, it is fine, could be just the alternator needs to up rpms to charge the battery correctly, etc.. its fine

did u allow it to warm up? Mine will jump around if I drive cold. It is something the engine does on its own to warm up, it kinda revs itself to warm up. It will usually sit around 850 when mine is at normal operating temp. Start it for a few, then drive.

If it does that sometimes, that should be normal, especially when the engine is thickened due to cold temperature. Plus, when you come to hard stop, the fluids slush around a bit, which might also cause the slightly higher idle rpm.