Do hot humid days help prevent facial wrinkles?

Not directly: A hot humid day might cause you to say indoors, and thus avoid sun exposure. Sun damage contributes significantly to skin aging. So, indirectly this would help prevent facial wrinkles. Keeping the skin well hydrated helps minimize wrinkles. Therefore the high humidity can be of some help. The best prevention is probably to use good sun care (sunscreens, hats, topical antioxidants, etc).

No: Moisture is good for your skin in creams. But, sun exposure, gravity, smoking, and facial expressivity are the most important factors in facial wrinkling.