Portland weather in December
In December, Portland has daytime highs averaging 7.9 °C, nights around 2.0 °C, with 18 wet days. Figures are 1991–2020 climate normals.
- 7.9°C Average high
- 2.0°C Average low
- 18days Wet days
- 194mm Rainfall
- 8.7h Daylight
Daily temperatures through December
How December develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 December | 8.1 °C | 2.3 °C | 53 % |
| 11–20 December | 8.0 °C | 2.3 °C | 63 % |
| 21–31 December | 7.6 °C | 1.6 °C | 56 % |
- Rain is most likely over days 11–20 of December (63 % of days) and least likely over days 1–10 (53 %).
What to expect
| Measure | Typical December | Share of the month |
|---|---|---|
| Days above 25 °C | 0 of 31 | 0 % |
| Days above 30 °C | 0 of 31 | 0 % |
| Days below 0 °C | 8.8 of 31 | 28 % |
| Days with more than 1 mm rain | 18 of 31 | 57 % |
Conditions in December
| Measure | Average |
|---|---|
| Mean temperature | 4.4 °C |
| Record high (1991–2020) | 15 °C |
| Record low (1991–2020) | -8.2 °C |
| Relative humidity | 86 % |
| Wind speed | 15 km/h |
| Cloud cover | 78 % |
December compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| January | 8.5 °C | 168 mm | 77 % |
| February | 10.5 °C | 130 mm | 72 % |
| October | 17.7 °C | 107 mm | 60 % |
| November | 11.3 °C | 175 mm | 74 % |
| December | 7.9 °C | 194 mm | 78 % |
See all twelve months for Portland
- December is the 12th warmest month here.
- It is the 12th driest month of the year.
- It ranks 12th for least cloud cover.
- Days last about 8.7 hours from sunrise to sunset.
- It rains on 18 of 31 days — 57 % of the month.
- Nights are about 5.8 °C cooler than the middle of the day.
- The hottest December day on record since 1991 reached 15 °C, 7.2 °C above the usual daytime high.
QuestionsDecember in Portland, answered
How warm is Portland in December?
Daily highs average 7.9 °C and nights fall to about 2.0 °C, a spread of 5.8 °C between afternoon and dawn. That makes December the 12th warmest month of the year here.
Does it rain much in Portland in December?
December averages 194 mm of rain, spread over about 18 of the 31 days — 57 % of the month. Cloud cover averages 78 % of the sky.
How long are the days in December?
Portland averages 8.7 hours between sunrise and sunset in December. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.