HEy actually you can break it in in the winter if you want, and take the propper precautions. Ive broke in a lot of my RC cars in winter time.

take a piece of aluminum foil, and a hair dryer. Heat up the Cooling head maily. but heat up the entire block untill its pretty darn hot. then tightly wrap the aluminum foil over the head to keep the heat in, and then break it in like normal. Run your first tank. do your cool off period. then take it back inside and reheat the head, and recover with foil and do the next tank. Trick works perfect.

ive done i think 5 motors this way. including my current one which has still be running strong a year later. good luck! and nice choice on a new truck!