Effects of high humidity. Humidity is considered too high when its level goes above 45% - 50%, sometimes as high as 80% and up. High humidity can be especially dangerous when combined with high temperature - as mentioned above, high humidity disrupts the body's ability to cool itself, which may lead to a heat stroke.
The average sea surface temperature in April 2017 for Cancun was 84.0Â°F. The maximum and minimum values were 83.0Â°F and 85.4Â°F respectively.
Cancun weather in May through September is the warmest time to visit when the average high temperature exceeds 90 degrees each month -- peaking at 92.5 in August. Cancun weather in December, January and February is coolest when the average high temperatures are about 83 degrees.