Isla Mujeres weather in September

Forum posters describe September as hot and humid, commonly around 30C by day and 23C overnight, and squarely inside the wet/hurricane season - though real experience varies a lot year to year, with some visitors seeing hardly any rain and others hitting a stretch of overcast, rain-every-2-3-days conditions. One long-time repeat visitor said that across more than a decade of September trips, they could hardly recall an activity actually ruined by rain, since showers typically run just 15-30 minutes before clearing back to sun. Posters are consistent that daily forecasts predicting rain often don't fully pan out, so the practical advice is to prepare for possible brief showers - and enjoy the dramatic sunsets the afternoon clouds tend to produce - rather than expecting a washed-out day.

Regulars are specific this falls just before hurricane season starts, typically meaning little rain and, by several accounts, no tropical storms encountered at all this month. Our row backs that hot, genuinely wet read, 30.8C reading as a scorching 36C, over 24.8C nights feeling 28C, with 84.2mm of rain across 11.3 days and humidity at 79 percent. Regulars are consistent the water itself reads as the warmest of the year so far, noticeably warmer than March or April, and the island stays meaningfully less busy than peak season. This remains genuinely less humid than the following July and August, hot but still manageable for beach and pool time. The sea sits at a bath-warm 27.5C. The record: 11.7 hours of sun, a 19.4 kph wind and AQI 47.

January on this coast belongs to the nortes, and the board describes them precisely: strong north winds running from about mid-December through February, lasting two or three days at a time, at their worst in January and February. They churn the water, drop the air temperature and make swimming less inviting; they close the harbour to the fishermen but rarely stop the ferry, which simply becomes a rocky ride. Our row carries the average rather than the event - 20.1 kph of wind, 26.9C reading as 29C, nights at 20.1C, and a sea still at 26.6C between fronts. Rain is 52.6mm across 11.5 days. The record: humidity 78 percent, 9.1 hours of sun and AQI 44.

December splits at the middle, and both halves of the split point the same way. The nortes start around mid-December and run to February, usually two or three days at a time, with a bad one meaning five days near 60F of wind and rain - which is why regulars name November and early December as their favourites. High season also begins about a week before Christmas and runs to the end of March, with New Year weekend the busiest, though they add that the crowds here stay manageable in a way Playa del Carmen's do not. Days are high-70s to low-80s with low humidity and a sweater wanted after dark; our row gives 27.7C over 21.1C. The record: 63.4mm across 11.6 days, 9.3 hours of sun and a 27.3C sea.

February is norte season and regulars will not pretend otherwise: the cold fronts run from about mid-December through February and are at their worst now, arriving with wind and rain, usually lasting two or three days, and generally shutting down the water activities while they blow. Some Februaries are gorgeous and some are windy and cool. Two things they say to settle nerves. The ferries do not cancel for a norte - hurricanes yes, this no - and the island has a sheltered side: the Cancun-facing west stays warmer and calmer while the east takes it. Our row gives 27.8C over 21.1C reading as 30C, with 30.1mm across 7.4 days and a 20.4 kph average that a norte week would double. Nights can feel chilly. The record: humidity 78 percent, 9.8 hours of sun and a 26.8C sea.