Weather in Portland in December

The month to avoid. December is the month most people should skip in Portland. Highs sit at 7.7 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 12 of 12 — near the bottom of Portland's year. July is the month that works, and the swing between the two is 63 points, which is a different holiday rather than a slightly better one.

Rain on 20 of the month's 31 days, 9 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Layers, and a genuinely waterproof outer — at 7.7 °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: 8 nights fall below freezing; the day barely swings — 5.6 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 17.5 °C and the coldest night fell to -10.9 °C, and the wettest single day dropped 74 mm — roughly 29% of the month's rain in one day.

December is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest December on record still delivered 484 mm against 123 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 251 mm average is a reasonable planning figure, not a promise.

Wind is light at 2.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 92%, which at 7.7 °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: 11.6 °C in November, 7.7 here, 8.5 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Portland's year — 8.7 hours of daylight against 15.7 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

With no coast nearby, the year swings a fair way — 27.7 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

December in Portland versus nearby

If Portland is one option among several, the nearby comparison is worth making. Eugene is close enough to be a coin toss — within a degree on temperature, the same number of rain days. Seattle is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: December is a compromise. July is 63 points better and is what Portland 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 Portland

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