Hillsboro weather in September: Hillsboro, Oregon: normal highs, lows, rain and records for September
Hillsboro in September has a normal high of 76°F and a normal low of 48°F, a daily mean of 62°F, falling from 80°F on the 1st to 71°F by the 30th. Measurable precipitation falls on 8 days in a normal September, 1.38 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 9°C, 35 mm of precipitation in September.
- NOAA stationPortland-Hillsboro Airport
- Station IDUSW00094261
- Location45.54°N 122.95°W
- Elevation204 ft (62 m)
- Population110,337
- Jan 47° 34°
- Feb 51° 34°
- Mar 56° 37°
- Apr 61° 39°
- May 69° 45°
- Jun 74° 49°
- Jul 82° 52°
- Aug 82° 52°
- Sep 76° 48°
- Oct 64° 41°
- Nov 53° 37°
- Dec 46° 33°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Hillsboro in September?
The normal high is 76°F and the normal low 48°F, for a daily mean of 62.0°F. September is 5.1°F cooler than August and 9.7°F warmer than October. September is the 3rd warmest month of the year in Hillsboro and the 9th wettest. Across the month the normal high falls 9°F, from 80°F on September 1 to 71°F on September 30. From one year to the next September's mean temperature typically moves about 2.0°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 60°F and 64°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 36%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 80°F | 50°F | 19% | 7% |
| September 8 | 79°F | 49°F | 22% | 9% |
| September 15 | 77°F | 48°F | 26% | 11% |
| September 22 | 75°F | 46°F | 31% | 14% |
| September 30 | 71°F | 44°F | 36% | 17% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 80°F | 50°F | 19% | 7% | 13 h 20 min |
| September 2 | 80°F | 50°F | 19% | 7% | 13 h 20 min |
| September 3 | 80°F | 50°F | 20% | 7% | 13 h 10 min |
| September 4 | 80°F | 50°F | 20% | 8% | 13 h 10 min |
| September 5 | 80°F | 49°F | 21% | 8% | 13 h 10 min |
| September 6 | 79°F | 49°F | 21% | 8% | 13 h 10 min |
| September 7 | 79°F | 49°F | 22% | 9% | 13 h |
| September 8 | 79°F | 49°F | 22% | 9% | 13 h |
| September 9 | 79°F | 49°F | 23% | 9% | 13 h |
| September 10 | 78°F | 49°F | 23% | 10% | 12 h 50 min |
| September 11 | 78°F | 49°F | 24% | 10% | 12 h 50 min |
| September 12 | 78°F | 48°F | 24% | 10% | 12 h 50 min |
| September 13 | 78°F | 48°F | 25% | 11% | 12 h 40 min |
| September 14 | 77°F | 48°F | 26% | 11% | 12 h 40 min |
| September 15 | 77°F | 48°F | 26% | 11% | 12 h 40 min |
| September 16 | 77°F | 48°F | 27% | 12% | 12 h 30 min |
| September 17 | 76°F | 47°F | 28% | 12% | 12 h 30 min |
| September 18 | 76°F | 47°F | 28% | 12% | 12 h 30 min |
| September 19 | 76°F | 47°F | 29% | 13% | 12 h 20 min |
| September 20 | 75°F | 47°F | 29% | 13% | 12 h 20 min |
| September 21 | 75°F | 47°F | 30% | 13% | 12 h 20 min |
| September 22 | 75°F | 46°F | 31% | 14% | 12 h 10 min |
| September 23 | 74°F | 46°F | 31% | 14% | 12 h 10 min |
| September 24 | 74°F | 46°F | 32% | 15% | 12 h 10 min |
| September 25 | 73°F | 46°F | 32% | 15% | 12 h 10 min |
| September 26 | 73°F | 45°F | 33% | 15% | 12 h |
| September 27 | 72°F | 45°F | 34% | 16% | 12 h |
| September 28 | 72°F | 45°F | 34% | 16% | 12 h |
| September 29 | 72°F | 45°F | 35% | 17% | 11 h 50 min |
| September 30 | 71°F | 44°F | 36% | 17% | 11 h 50 min |
- Normal high
- 76°FSeptember average
- Normal low
- 48°FSeptember average
- Precipitation
- 1.38 inmonth total
- Days with precipitation
- 80.01 inch or more
- Days at 90°F or more
- 2
- Daylight
- 13 h 20 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 22
- Days at 80°F or more
- 10
- Sunshine
- 78%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00094261; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Hillsboro in September?
On a given September day the chance of 0.01 inch or more is 27% on average, highest around September 30 (36%). In all, 1.38 in falls on 8 days of a normal September.
In a normal September in Hillsboro, 2 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00094261.
How humid and windy is Hillsboro in September?
At 3 p.m. the normal temperature is 70°F with 46% relative humidity and a dew point of 48°F; at 6 a.m. it is 48°F with 91% humidity. The wind averages 3.9 mph, most often from the north in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 48°F | 45°F | 91% | 2.1 mph | – |
| 9 a.m. | 57°F | 49°F | 76% | 3.2 mph | 52% |
| noon | 66°F | 49°F | 54% | 5.4 mph | 61% |
| 3 p.m. | 70°F | 48°F | 46% | 6.4 mph | 62% |
| 6 p.m. | 64°F | 49°F | 59% | 5.6 mph | 67% |
| 9 p.m. | 57°F | 49°F | 76% | 3.9 mph | 71% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00094261. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Hillsboro?
The warmest September temperature on Hillsboro's official record (since 1929) is 103°F, on September 3, 1988; the coldest is 29°F, on September 25, 1934. The wettest September brought 6.27 in (2013).
The September mean against the 1991-2020 normal of 62.0°F: 2021 62.2°F (+0.2), 2022 65.3°F (+3.3), 2023 62.4°F (+0.4), 2024 63.9°F (+1.9), 2025 65.4°F (+3.4), 2026 60.9°F (−1.1). 5 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 62.2°F | +0.2°F | 3.12 in |
| 2022 | 65.3°F | +3.3°F | 0.34 in |
| 2023 | 62.4°F | +0.4°F | 2.21 in |
| 2024 | 63.9°F | +1.9°F | 0.84 in |
| 2025 | 65.4°F | +3.4°F | 1.36 in |
| 2026 | 60.9°F | −1.1°F | 0.83 in |
Source: records: ACIS, NWS threaded record HIOthr; recent months: ACIS, station USW00094261. Records and recent months use complete months only.
How does September in Hillsboro compare across Oregon?
Across the 105 places PlainClimate covers in Oregon, September normal highs run from 64°F in Newport to 87°F in Cave Junction; Hillsboro's is 76°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.