Well, if the stuff re-freezes, you're not exactly better off, are you?
Would primarily depend upon ambient temperature and relative humidity, though - and remember that the water goes a lot of interesting places you cannot readily inspect, i.e. control cable housings etc. etc.
OTOH, as long as no other precipitation is falling, it should be relatively safe. Suggest you have a go and then inspect thoroughly, say, 20 min. after application.