Hillsboro, OR weather in September
Expect mild weather with some rain in Hillsboro in September, with highs near 76°F and lows near 49°F. Rain falls on about 6 days. Great for outdoor plans.
- Normal high
- 76°F
- Normal low
- 49°F
- Wet days
- 6
- 1.3 in total
- Muggy days
- 0
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 80°F | 71°F |
| Normal low | 51°F | 46°F |
| Chance of a wet day | 17% | 27% |
| Sunrise / sunset | 6:33 am / 7:50 pm | 7:09 am / 6:54 pm |
| Daylight | 13.3 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical September day
- 6 am50°Fdew point 48°F
- 9 am61°Fdew point 51°F
- Noon70°Fdew point 51°F
- 3 pm74°Fdew point 50°F
- 6 pm70°Fdew point 51°F
- 9 pm61°Fdew point 51°F
NOAA hourly normals (local standard time) from Portland-Hillsboro Airport (2 mi away); average wind 4 mph.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F16 of 30
- Hot dayshigh 90°F or more3 of 30
- Muggy daysdaily mean dew point 65°F or more0 of 30
- Wet daysat least 0.01 in of rain or melted snow6 of 30
- Notable rainat least 0.10 in3 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 1.3 in; a dry September brings about 0.6 in and a wet one about 1.5 in (25th and 75th percentiles). About 1 day brings half an inch or more.
How September varies from year to year
- Warmest September, 1991-20201993: average high 84°F
- Coolest September2019: average high 72°F
- Wettest September2013: 7.6 in
- Driest September1993: no measurable precipitation
- Highest reading103°F (September 1, 1998)
- Lowest reading33°F (September 27, 1999)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 82°F | 76°F | 63°F |
| Normal low | 54°F | 49°F | 42°F |
| Wet days | 3 | 6 | 12 |
| Comfortable days | 12 | 16 | 13 |
| Daylight | 14.1 h | 12.5 h | 10.9 h |
Highs change by -6°F from August and -13°F into October.
Nearby alternatives in September
- Drier: Bend, OR130 mi · high 76°F · 2 wet days
- Cooler: Cannon Beach, OR53 mi · high 68°F · 9 wet days
How Hillsboro ranks in September
- Normal high256th warmest of 378 cities; 3rd of 6 in Oregon
- Wet days118th driest of 378
- Comfortable days52nd most of 342
What to pack for Hillsboro in September
- Layers – afternoons near 76°F but nights near 49°F
Heating and cooling
September has 123 heating degree days and 45 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Hillsboro in September?
The normal high is 76°F and the normal low is 49°F. From 1991 to 2020 the hottest September reading was 103°F (September 1, 1998).
Does it rain a lot in Hillsboro in September?
About 6 days in September have at least 0.01 in of precipitation, and the normal total is 1.3 in. The wettest September in 1991-2020 was in 2013 (7.6 in); the driest was in 1993, with no measurable precipitation.
Is September a good time to visit Hillsboro?
September ranks 4th of 12 months on our comfort score for Hillsboro (70 out of 100). It has about 16 comfortable days and about 3 days at 90°F or hotter. The best month is June.
Where the numbers come from
- Temperature and snow depth: Forest Grove (USC00352997), 5.5 mi W of the city center, 180 ft . NOAA normals and daily records, 1991-2020.
- Rain and snowfall: Dilley 2 S (USC00352325), 7.3 mi SW of the city center, 194 ft . NOAA normals and daily records, 1991-2020.
- Frost dates and humidity and wind by hour: Portland-Hillsboro Airport (USW00094261), 2.3 mi ENE of the city center, 204 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Portland International Airport (726980-24229), 19 mi ENE of the city center, 22 ft (173 ft lower than the city). Hourly observations, 1991-2020.
- Not available for this location: cloud cover (no station close enough or similar enough in elevation).