Climate averages 1991–2020
Hillsboro weather
in December.
A cold, very wet month: the coolest and the wettest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a cold month in Hillsboro: daytime highs average 7.4°C and nights cool to about 1.7°C. By daytime temperature it is the coolest month of the year.
Expect about 204 mm of rain on roughly 18 days, which makes December a very wet month (the wettest month of the year). Daylight, from sunrise to sunset, lasts about 8 h 47 min on an average December day.
The nearest other city in this atlas is Beaverton (15 km away). In December its highs average 7.3°C, about as warm as Hillsboro, with 193 mm of rain.
Among the 498 cities listed in the United States, Hillsboro ranks joint 290th of 498 for the warmest December highs and 492nd of 498 for the driest December (rainfall, lowest first). The mean December high of those 498 cities is 10.5°C; Hillsboro is 3.2°C cooler than that mean.
From December to January, average highs rise by 0.5°C to 7.9°C, and monthly rainfall falls from 204 mm to 172 mm.
The annual picture
December in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Hillsboro climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 7.9°C1.8°C | 1.8°C | 172 | 17.1 | 9.19 h |
| February | 9.7°C2.1°C | 2.1°C | 133 | 14.4 | 10.310 h |
| March | 12.1°C3.5°C | 3.5°C | 151 | 17.3 | 11.912 h |
| April | 14.6°C5.2°C | 5.2°C | 115 | 15.6 | 13.513 h |
| May | 18.6°C8.4°C | 8.4°C | 69 | 10.6 | 14.915 h |
| June | 21.5°C11.0°C | 11.0°C | 40 | 7.2 | 15.616 h |
| July | 26.6°C13.8°C | 13.8°C | 11 | 2.2 | 15.315 h |
| August | 27.1°C14.4°C | 14.4°C | 13 | 2.5 | 14.114 h |
| September | 23.7°C12.2°C | 12.2°C | 43 | 6.0 | 12.613 h |
| October | 16.7°C8.0°C | 8.0°C | 107 | 11.5 | 11.011 h |
| November | 10.7°C4.2°C | 4.2°C | 179 | 17.3 | 9.610 h |
| December, selected | 7.4°C1.7°C | 1.7°C | 204 | 17.5 | 8.89 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
December in nearby cities
- Beaverton in DecemberUnited States · 15 kmHigh 7.3°C · Low 1.5°C · 193 mm rain
- Portland in DecemberUnited States · 24 kmHigh 7.7°C · Low 1.7°C · 193 mm rain
- Vancouver, United States in DecemberUnited States · 29 kmHigh 7.2°C · Low 1.3°C · 231 mm rain
- Gresham in DecemberUnited States · 44 kmHigh 6.8°C · Low 1.0°C · 244 mm rain
- Salem, United States in DecemberUnited States · 65 kmHigh 8.1°C · Low 1.9°C · 181 mm rain
- Eugene in DecemberUnited States · 164 kmHigh 8.2°C · Low 1.2°C · 206 mm rain
- Tacoma in DecemberUnited States · 197 kmHigh 6.7°C · Low 1.8°C · 174 mm rain
- Federal Way in DecemberUnited States · 207 kmHigh 6.2°C · Low 1.1°C · 196 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Hillsboro) is explained once on the Hillsboro year overview and on the Sources, method and limits page.