Yes, you should reschedule. Heat is not great for fresh botox. For the first 48-72 hours, you should avoid: intense heat (saunas, steam rooms, hot tubs, and direct intense sun), heavy exercise that raises body temperature, and anything that increases blood flow to the face (facials, massages). The heat can cause the product to metabolize faster, potentially reducing how long it lasts. Also, if you get sunburned, that inflammation can also affect the results. If you get botox the day before a beach vacation, you'll be spending your vacation avoiding the sun and not sweating. That's no fun. Do it when you return, or do it a week before so the product has settled.