Weather in Miami in September

Shoulder season. September is shoulder season in Miami — cheaper, quieter, and a genuine gamble. You should expect rain on 26 days of the month, which is more days wet than dry.

September ranks 10 of 12 — near the bottom of Miami's year. January is the month that works, and the swing between the two is 35 points, which is a different holiday rather than a slightly better one.

Rain on 26 of the month's 30 days, 5 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. Pack for 29.3 °C days and 27.5 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 6 days top 30 °C — hot spells arrive, but they break; the day barely swings — 1.8 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 31.5 °C and the coldest night fell to 23.2 °C, and the wettest single day dropped 108 mm — roughly 57% 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 326 mm against 74 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 189 mm average is a reasonable planning figure, not a promise.

Wind is light at 13.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 78%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 30 °C in August, 29.3 here, 27.9 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 9 days less of it, so pushing the dates later buys drier weather.

Daylight in September

12.3 hours of daylight, losing 0.7 hours across the month. That is between Miami's extremes of 13.7 and 10.5 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 29.3 °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 Miami versus nearby

If Miami is one option among several, the nearby comparison is worth making. Cape Coral is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Key West is close enough to be a coin toss — within a degree on temperature, 3 days less rain.

So: September is a compromise. January is 32 points better and is what Miami 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 Miami

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