It's not a matter of the overnight temp, it's a matter of whether or not A/C is in use where you'll be sleeping. I keep my house thermostat at 76*F but I have to be cognizant of where the air ducts are as the cooled air comes out around 60-65*F - you don't want your BP sitting by that all night.
Ok, I'll make sure he's in a warm spot and ask the friend I'm staying with to not have the AC so cold. What do I have to worry about if he gets too cold... RI? Worse?