I was on a ~300 miles trip and it was definitely below 50 degrees. I stopped to have a snack and a refill. During the stay I turned on the heater which was previously off. When I moved again, after doing a few miles I noticed that the engine temperature started to fall and it started to misfire. The condition continued to worsen as the needle went down.
So I turned off the heater, stopped for a while and allowed the engine to re-gain heat by paddling gas. This kept on happening again and again.
What could possibly be the cause of this