Kevin, he's spraying his final coats. Primer is done.
Mike, check with your paint manufacturer. Most offer different speed reducer/activators for temperature. I sprayed plenty of times at 4 in the morning, knowing that the natural oven will help cure it later in the day. More important, it seems, is not the ambient temperature, but the substrate temperature. I always have a temp gun with me and the moment my surface I'm going to spray, hits the mid 70's, I'll start to apply paint. Checking between coats. Plenty of times the air has been in the 60's, but the metal temp was the proper temp for spraying.
