Are you going to cancel your trip if its bad. lol They can't predict the weather any better in Mexico .
No cancelation from this house last trip rained everyday and still had time of my life rain drinks and the sexy pool equal hot times
I've also had trips that rained alot, gladly it doesn't happen too often worst was 10/14 days of bad weather, but you make the most of it Best was 14/14 of sun sun in Negril. I smiled for 6 months Ive learned that Mexican forecasts are highly unpredictable and depressing cause they always call for rain and then it doesn't or just for minutes. So I just try not to look. Drink enuf tequila and the sun will shine
Best ever was 21/21 sunny days in Icmeler, Turkey, over 100 degrees as well. If Cancun can compare with that I'll be well happy.
Keep this link to check on Cancun weather anytime! Hope it helps! Cancun Weather Forecast and Conditions