I try to spray when temp. is 20 - 30 c. but if it is humid I will postpone . I find when humid it takes longer to dry . I always tell people to stay off driveway for minimum 48 hours . If driveway is still tacky after 2 days I tell them to run garden hose on it for 20 minutes , only had a couple drives like that . I say it was combination of humid temp. and spray too thick.. I would sooner postpone then have someone track into there house.. Some people can hardly wait 24 hours.. Plus when it is real humid I have more fun in my cool basement having a beer.