I just had the same thing happen to me. I don't know if the game runs through some cycle, and if you end the game when winter is about to come, then your next new game will start at winter. I restarted my run, just before winter was about to arrive, and suddenly my next 10 restarts was day 1 winter scenarios. I just tried ending days, staying home at night for as long as my people could survive. I survived for 8 days, and suddenly I was getting normal temp start up scenarios. If this did the trick, or it was just pure randomness or luck, I don't know