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.
You both have really nothing to worry about! The weather in Cancun in April will be just great, but a little warmer than January, February or March. But you will have a blast, the tropical showers do not start in April, but, you may have a day or so when it rains for 15-30 minutes, then again, full sun. Go and enjoy!