I like to look at weather web sites that provide hour-by-hour forecasts. That helps to determine what to wear/pack on a vacation. You can tell if the temperatures are likely to drop significantly at night. Helps me figure out whether I'll need a jacket /hoodie.
Also, remember that even if the temps are hot outside, restaurants, shops, and attractions at WDW are heavily air-conditioned. I've learned to pack a light sweater (in my backpack) because it can seem very chilly indoors after the heat and humidity outside.