Weather in Bilbao in December

Shoulder season. December is shoulder season in Bilbao — cheaper, quieter, and a genuine gamble. Highs sit at 13.4 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 10 of 12 — near the bottom of Bilbao's year. July is the month that works, and the swing between the two is 43 points, which is a different holiday rather than a slightly better one.

Rain on 14 days, 4 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 13.4 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 3.7 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 19.5 °C and the coldest night fell to 0.5 °C, and the wettest single day dropped 42 mm — roughly 35% of the month's rain in one day.

December is moderately variable: 12 mm in the driest year against 344 mm in the wettest, around an average of 120 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind sits around 18.6 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 79%, which at 13.4 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

Temperatures hold steady either side: 15.7 °C in November, 13.4 here, 12.5 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Bilbao's year — 9 hours of daylight against 15.4 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 14.1 °C in December — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 21.9 °C in August and bottoms out at 12.5 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

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.

December in Bilbao versus nearby

If Bilbao is one option among several, the nearby comparison is worth making. Gasteiz / Vitoria is the weaker option in December — 3.7 °C cooler, the same number of rain days. Gijón is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: December is a compromise. July is 35 points better and is what Bilbao 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 Bilbao

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