Weather in Leiria in December

Shoulder season. December sits in between. You will get good days and you will lose some. Highs average 15.4 °C, lows 6.8 °C, and rain falls on 11 days — nothing in the month is working against you.

December ranks 11 of 12 — near the bottom of Leiria's year. June is the month that works, and the swing between the two is 32 points, which is a different holiday rather than a slightly better one.

Rain on 11 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 15.4 °C days and 6.8 °C nights; the spread matters more here than any single number.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest December day reached 20.7 °C and the coldest night fell to -2.6 °C, and the wettest single day dropped 34 mm — roughly 45% of the month's rain in one day.

December is moderately variable: 20 mm in the driest year against 191 mm in the wettest, around an average of 76 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 7.3 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 85%, high enough to notice on the warm days without dominating them.

How December sits in the year

Temperatures hold steady either side: 18.1 °C in November, 15.4 here, 14.9 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Leiria's year — 9.4 hours of daylight against 15 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 15.9 °C in December — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 19.9 °C in August and bottoms out at 14.3 °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 Leiria versus nearby

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

So: December is a compromise. June is 29 points better and is what Leiria 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 Leiria

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