Weather in Lisbon in December

A good month. December is a solid month to be in Lisbon. Highs average 15.1 °C, lows 11.5 °C, and rain falls on 10 days — nothing in the month is working against you.

December ranks 10 of 12 — near the bottom of Lisbon's year. July 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. Worth keeping in perspective: December is the weakest month of Lisbon's year and it is still a perfectly good one. The downside here is small.

Rain on 10 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 15.1 °C days and 11.5 °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: the day barely swings — 3.6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 18.3 °C and the coldest night fell to 5 °C, and the wettest single day dropped 29 mm — roughly 45% of the month's rain in one day.

December is moderately variable: 15 mm in the driest year against 177 mm in the wettest, around an average of 65 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind sits around 17.8 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 82%, high enough to notice on the warm days without dominating them.

How December sits in the year

Temperatures hold steady either side: 17.1 °C in November, 15.1 here, 14.4 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Lisbon's year — 9.5 hours of daylight against 14.9 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 16.9 °C in December — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 20.7 °C in September and bottoms out at 15.3 °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 Lisbon versus nearby

If Lisbon is one option among several, the nearby comparison is worth making. Évora is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Leiria is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: December is a compromise. July is 32 points better and is what Lisbon 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 Lisbon

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