I don't think the engines mind the cold as much as the pilots. Like you've already been told, just richen up the needle a bit. The worst part is holding your hand in the prop blast while you tune the engine. That, and scraping off the frozen exhaust residue after you fly.

It's worth it, though. The planes fly great in the cold, still, dense air. Plus, you never have to wait your turn to fly.

Have fun

PS - Watch your batteries!!! You will get about half as many flights on a cold battery as you would normally get during the summer. Check your RX battery after every flight.