Weather in Cancun. The average temperature in Cancun is 80F (26C). January and February are the coolest months; June and July are the hottest. Even though the temperature does not vary that much throughout the year, there are 2 distinct seasons in Cancun. The wet (rainy) season is May to October and it is slightly hotter. Cancun's dry season is November to April. It is much cooler also. The best time of year to travel to Cancun (weather-wise) is during the dry season's coolest months: January and February. March and April are the driest months of the year, and also the sunniest months in Cancun. Humidity is high in Cancun, often around 80%. April and May have the lowest humidity.