It is too hot. If the weather is too hot, then the paint tends to dry too fast. If this is the case, it can bubble up also. Do not spray paint directly in the beating sun (especially in the summer) or your paint will bubble right up.
not the charm for me, but I’m pretty sure the next time I’ll be more successful because I made ALL THE MISTAKES possible already. Spray painting tips (borrowed from Krylon’s website; my DON’Ts are in green): Choose your location.