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.
Expect 109mm (4.3 inches) of rainfall across the whole of May with 7 days with some rain falling. Maximum UV levels will be extreme (11+ UV index) at midday when the skies are clear. The average sea temperature in and around Cancun in May is 27Â°C (81Â°F). Cancun sunrise & sunset times for May 2018 Browse the sunrise & sunset times for Cancun in May 2018.