Climate averages 1991–2020
Hillsboro weather
in September.
A warm, moderately wet month: the 3rd warmest and the 4th driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Hillsboro: daytime highs average 23.7°C and nights cool to about 12.2°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 43 mm of rain on roughly 6 days, which makes September a moderately wet month (the 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 35 min on an average September day.
The nearest other city in this atlas is Beaverton (15 km away). In September its highs average 23.7°C, about as warm as Hillsboro, with 42 mm of rain.
Among the 498 cities listed in the United States, Hillsboro ranks joint 374th of 498 for the warmest September highs and 169th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Hillsboro is 3.1°C cooler than that mean.
From September to October, average highs fall by 7.1°C to 16.7°C, and monthly rainfall rises from 43 mm to 107 mm.
The annual picture
September 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, selected | 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 | 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
September in nearby cities
- Beaverton in SeptemberUnited States · 15 kmHigh 23.7°C · Low 12.0°C · 42 mm rain
- Portland in SeptemberUnited States · 24 kmHigh 24.1°C · Low 12.3°C · 42 mm rain
- Vancouver, United States in SeptemberUnited States · 29 kmHigh 23.5°C · Low 12.0°C · 62 mm rain
- Gresham in SeptemberUnited States · 44 kmHigh 22.8°C · Low 11.3°C · 58 mm rain
- Salem, United States in SeptemberUnited States · 65 kmHigh 24.5°C · Low 12.0°C · 32 mm rain
- Eugene in SeptemberUnited States · 164 kmHigh 24.3°C · Low 11.3°C · 41 mm rain
- Tacoma in SeptemberUnited States · 197 kmHigh 20.8°C · Low 11.9°C · 50 mm rain
- Federal Way in SeptemberUnited States · 207 kmHigh 20.3°C · Low 11.2°C · 64 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.