Is this an enamel thing with rain?
Enamels act stupid, bead up, refuse to dry, refuse to cover, you name it.
Laquers simply "blush" and refuse to gloss up. They go on then develop a white pasty appearence. Being laquers, this penetrates all the coats as they merge into one anyway.
Acrylics spray better with a touch of moisture in the air but there is definately a sweet spot as stated by Bill.