Weather in San Luis Potosí in September

A good month. September is a solid month to be in San Luis Potosí. Highs average 25.6 °C, lows 13.7 °C, and rain falls on 14 days — nothing in the month is working against you.

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

Rain on 14 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average September reaches 30 °C. Across the twenty years measured, the hottest September day reached 30.8 °C and the coldest night fell to 7.2 °C, and the wettest single day dropped 28 mm — roughly 30% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 162 mm against 44 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 94 mm average is a reasonable planning figure, not a promise.

Wind is light at 11.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 75%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 27.1 °C in August, 25.6 here, 25 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 8 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 San Luis Potosí's extremes of 13.5 and 10.8 hours, so days are long enough not to constrain the plan.

An inland climate

Despite being inland, the year stays fairly even: 24.5 °C between the year's warmest afternoons and coldest nights. At 1886 m, altitude is doing as much work here as latitude: thinner air means fierce sun by day and heat that leaves the moment it sets.

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 San Luis Potosí versus nearby

If San Luis Potosí is one option among several, the nearby comparison is worth making. Santiago de Querétaro is close enough to be a coin toss — within a degree on temperature, 5 days more rain. Morelia is close enough to be a coin toss — within a degree on temperature, 11 days more rain.

So: September is a compromise. December is 25 points better and is what San Luis Potosí 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 San Luis Potosí

See all twelve months in San Luis Potosí, or where else to go in September.