Weather in Jacksonville in September

Shoulder season. September is shoulder season in Jacksonville — cheaper, quieter, and a genuine gamble. You should expect rain on 16 days of the month, which is more days wet than dry.

September ranks 9 of 12 in Jacksonville: past the worst of the year but short of November, which is the month to book if the dates are open.

Rain on 16 days, 5 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 30.7 °C days and 21.8 °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: 19 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest September day reached 37.9 °C and the coldest night fell to 12.3 °C, and the wettest single day dropped 115 mm — roughly 78% of the month's rain in one day.

September is moderately variable: 46 mm in the driest year against 402 mm in the wettest, around an average of 147 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 2.2 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 81%, high enough to notice on the warm days without dominating them.

How September sits in the year

The month is on the way down: 1.9 °C cooler than August, with October dropping another 3.4 °C. The first week and the last are not the same trip. Rain is the thing that moves: October brings 6 days less of it, so pushing the dates later buys drier weather.

Daylight in September

12.4 hours of daylight, losing 0.9 hours across the month. That is between Jacksonville's extremes of 14.1 and 10.2 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 28.1 °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

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

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

September in Jacksonville versus nearby

If Jacksonville is one option among several, the nearby comparison is worth making. Tallahassee is close enough to be a coin toss — within a degree on temperature, 3 days less rain. Tampa is close enough to be a coin toss — within a degree on temperature, 6 days more rain.

So: September is a compromise. November is 36 points better and is what Jacksonville 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 Jacksonville

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