Weather in Bilbao in September

Prime time. If you get to pick your dates, September is the one. Highs average 22.6 °C, lows 18.3 °C, and rain falls on 9 days — nothing in the month is working against you.

September ranks 4 of 12 in Bilbao: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 9 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; the day barely swings — 4.3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 31.7 °C and the coldest night fell to 13.4 °C, and the wettest single day dropped 45 mm — roughly 85% of the month's rain in one day.

September is moderately variable: 16 mm in the driest year against 105 mm in the wettest, around an average of 53 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 12.8 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 72%.

How September sits in the year

Temperatures hold steady either side: 24.1 °C in August, 22.6 here, 20.3 in October. Nothing about the timing within the month matters much.

Daylight in September

12.6 hours of daylight, losing 1.4 hours across the month. That is between Bilbao's extremes of 15.4 and 9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 20.9 °C in September — swimmable, but it takes a moment to commit. This is the warmest the water gets all year.

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 Bilbao versus nearby

If Bilbao is one option among several, the nearby comparison is worth making. Gasteiz / Vitoria is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Gijón is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: September is effectively as good as it gets here — 2 points behind July, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Bilbao

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