Weather in Mérida in September

A hard month. September asks something of you. Go in knowing what. You should expect rain on 23 days of the month, which is more days wet than dry.

September ranks 8 of 12 in Mérida: past the worst of the year but short of January, which is the month to book if the dates are open.

Rain on 23 of the month's 30 days, 6 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Natural fibres and a second shirt for the day. At 85% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 20 days top 30 °C, making the heat continuous rather than occasional. Across the twenty years measured, the hottest September day reached 36.5 °C and the coldest night fell to 21.3 °C, and the wettest single day dropped 156 mm — roughly 83% of the month's rain in one day.

September is moderately variable: 75 mm in the driest year against 555 mm in the wettest, around an average of 188 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 0.7 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 85% is the real story though — it is the number that decides how the day feels, not the 31 °C.

How September sits in the year

Temperatures hold steady either side: 32.3 °C in August, 31 here, 29.9 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 7 days less of it, so pushing the dates later buys drier weather.

Daylight in September

12.3 hours of daylight, losing 0.6 hours across the month. That is between Mérida's extremes of 13.4 and 10.9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 29.1 °C in September — warm enough that the water offers no relief from the heat. This is the warmest the water gets all year.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Mérida versus nearby

If Mérida is one option among several, the nearby comparison is worth making. Cancún is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Key West is a better bet in September — within a degree on temperature, the same number of rain days.

So: September is a compromise. January is 36 points better and is what Mérida is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Mérida

See all twelve months in Mérida, or where else to go in September.