I’m guessing that the fan is inoperable. Start by bypassing the temperature sensor to see if the fan spins?
It was only 45* today.
I would check the fan, it's easy, eliminate the simple first, as it's hard to belive it actually got hot too on a 45° day.
I would check for low coolant, or an air pocket, if there is an actual heating issue, or maybe the temperature sensor giving a bad reading.
Thermostats go bad too, but it's not common.
Have you ever flushed the coolant in it?