Weather in Lille in September

Prime time. If you get to pick your dates, September is the one. Highs average 20.2 °C, lows 10.3 °C, and rain falls on 11 days — nothing in the month is working against you.

September ranks 2 of 12 in Lille. Only June scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 11 days, 1 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 31.5 °C and the coldest night fell to 3.3 °C.

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 122 mm against 18 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 52 mm average is a reasonable planning figure, not a promise.

Wind is light at 9.5 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: 2.7 °C cooler than August, with October dropping another 4.3 °C. The first week and the last are not the same trip.

Daylight in September

12.7 hours of daylight, losing 1.9 hours across the month. That is between Lille's extremes of 16.4 and 8 hours, so days are long enough not to constrain the plan.

An inland climate

Despite being inland, the year stays fairly even: 22.6 °C between the year's warmest afternoons and coldest nights.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

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

September in Lille versus nearby

If Lille is one option among several, the nearby comparison is worth making. Breda is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Rotterdam is close enough to be a coin toss — within a degree on temperature, 2 days more rain.

So: September is effectively as good as it gets here — 0 points behind June, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Lille

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