Bob brings up a good point about wax and grease removers that needs to be expounded on.
Even though you wipe the wax and grease remover dry as you do each panel
that does not mean it is out of all the pores be it metal or primer.
High humidity will further slow the evaporation rate as well as a cool shop.
Some painter will use a blow gun as they tack the car to help dry and some will let the car set for 15 to 20 minutes to finish drying.
What you don't see can be a disaster if it is not dry.