The average daytime temperature in Cancun is 80º F, with only about a five degree variation year-round. Unlike the rest of mexico, the rainy season here is during the late fall and winter months. It can sometimes even get chilly at night; lightweight sweaters, jackets or shawls are recommended for cool winter evenings. The summer months are generally hot and humid with frequent but brief showers.

Cancun has an average of more than 200 sunny days a year and has less annual rainfall than the Virgin Islands or the Bahamas. While it is not directly within the Caribbean hurricane belt, the old Mexican adage "hurricanes have no helm" sometimes applies. You may run into some rain, overcast weather and days with bothersome wind gusts. Usually a light breeze blows across the island, keeping things cool.

Red or yellow flag warnings are common on the open-sea side of the island, and swimming there is not recommended. Black flag wrnings are posted at especially treacherous spots.

What to wear? Strictly casual resort wear, especially during the day. Jackets and ties are never needed, but it is customary to dress up for the discos, and most nice restaurants and bars require men to werar shirts and slacks (some allow Bermudas). Most frown on sandals. Women are allowed more leeway, but would likely feel under-dressed in tank tops and flip-flops.