Ugh I need help before I lose my sanity

My two year old recently will wake up sometimes in the middle of night or mornings with a runny/sneezy nose. We do leave his ceiling fan running because if not it gets too hot.

(We recently moved to a state that doesn't seem to believe in AC because it has more winter months than summer 🙃)

But it's not like he's getting cold, or getting sick. It's just like when he sleeps he wakes up congested and then after awhile he's over it. We've tried leaving the fan off but then he wakes up too hot. I don't even know if the fan is the issue considering we've left it on all summer, and during his naps, and he's just now recently started this about a week-two weeks ago.

Any suggestions on what to do or what else could be the cause? We were also thinking maybe allergies but we literally haven't changed anything and again it only happens at night.