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: Annual Weather Averages. June is the hottest month in Cancun with an average temperature of 28Â°C (82Â°F) and the coldest is January at 23Â°C (73Â°F) with the most daily sunshine hours at 11 in August.The wettest month is September with an average of 270mm of rain.The best month to swim in the sea is in July when the average sea temperature is 29Â°C (84Â°F).he wettest month is September with an average of 270mm of rain. The best month to swim in the sea is in July when the average sea temperature is 29Â°C (84Â°F).