September
Other strong months: August and July
93/100 weather score
United States · 1991–2020
Best time to visit
Portland
For Portland, September has the most comfortable weather in our climate comparison. Typical daytime highs are 23.9°C, nights average 12.8°C, and rainfall totals about 41 mm. Figures use measured 1991–2020 normals from the nearest eligible NOAA station.
Best all-round monthSeptember
Typical daytime high23.9°C
Typical night-time low12.8°C
September rainfall41 mm
May
Other strong months: June and September
86/100 weather score
Make the answer personal
Choose the weather
that suits you.
Set the daytime temperature and rainfall you are comfortable with. We will show only the months that meet every choice, using the measured 1991–2020 averages below.
5 months fit your choices for Portland
The lowest comfort score is 5 out of 100. January and December share that score. In January, that is mainly because days reach only 8.4°C, 16° below the 24°C the score treats as ideal.
Quick answers
Planning a trip to Portland?
These answers come from the same measured monthly climate record shown on this page.
When is the best time to visit Portland?
September is the strongest all-round choice in our temperature-and-rainfall comparison, with a typical daytime high of 23.9°C and 41 mm of rain.
What is the hottest month in Portland?
August is hottest in this record, with a typical daytime high of 27°C and a night-time low of 14.8°C.
Which month has the least rain?
July has the lowest monthly rainfall total at 10 mm.
Is this a weather forecast?
No. These are long-term measured averages from 1991–2020. Check a current forecast before you travel.
Month by month
See how the weather
changes through the year.
The bars combine daytime temperature, night-time temperature and rainfall. The figures are measured historical averages, not a forecast for a particular trip.
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 8.4°C | 3.1°C | 158 mm | 16.2 | 9 h 04 | 5 | Strong coverage |
| February | 10.3°C | 3.7°C | 120 mm | 12.7 | 10 h 18 | 14 | Strong coverage |
| March | 13.1°C | 4.9°C | 124 mm | 15.3 | 11 h 46 | 23 | Strong coverage |
| April | 16°C | 6.7°C | 91 mm | 13.5 | 13 h 27 | 41 | Strong coverage |
| May | 20.1°C | 9.7°C | 64 mm | 9.5 | 14 h 52 | 67 | Strong coverage |
| June | 22.8°C | 11.9°C | 38 mm | 6.3 | 15 h 40 | 87 | Strong coverage |
| July | 26.9°C | 14.4°C | 10 mm | 2.3 | 15 h 21 | 89 | Strong coverage |
| August | 27°C | 14.8°C | 14 mm | 2.4 | 14 h 07 | 90 | Strong coverage |
| September | 23.9°C | 12.8°C | 41 mm | 5.3 | 12 h 28 | 93 | Strong coverage |
| October | 17.2°C | 8.9°C | 100 mm | 10.4 | 10 h 51 | 51 | Strong coverage |
| November | 11.3°C | 5.4°C | 163 mm | 15.9 | 9 h 26 | 11 | Strong coverage |
| December | 7.7°C | 2.9°C | 189 mm | 16.9 | 8 h 43 | 5 | Strong coverage |
What has changed
Recent daytime highs are
0.2°C warmer in Portland.
Each bar shows the difference between the 2011–2025 average daytime high and the 1961–1990 average for the same month at the same station. A blank month does not have enough older observations for a reliable comparison.
Jan
+0.6
Feb
-0.8
Mar
-0.7
Apr
-0.4
May
+0.8
Jun
+0.2
Jul
+1.1
Aug
+1.4
Sep
+0.3
Oct
-0.2
Nov
0.0
Dec
+0.5
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 18.3°C18 Jan 2005 | -11.1°C13 Jan 2024 | 64 mm31 Jan 2003 | 306 mm2006 · driest 7 mm in 1985 | 52 |
| February | 21.7°C28 Feb 1988 | -13.3°C3 Feb 1989 | 65 mm28 Feb 2011 | 316 mm1996 · driest 25 mm in 1993 | 52 |
| March | 27.8°C26 Mar 2025 | -4.4°C3 Mar 1989 | 51 mm12 Mar 2026 | 253 mm2012 · driest 44 mm in 1978 | 53 |
| April | 32.2°C19 Apr 2016 | -0.6°C1 Apr 2008 | 34 mm11 Apr 2022 | 179 mm2003 · driest 16 mm in 1977 | 53 |
| May | 39.4°C28 May 1983 | 2.2°C6 May 1978 | 38 mm31 May 1997 | 134 mm2013 · driest 3 mm in 1992 | 51 |
| June | 45.6°C28 Jun 2021 | 4.4°C10 Jun 2018 | 42 mm20 Jun 1991 | 122 mm2010 · driest 1 mm in 2003 | 53 |
| July | 40.6°C28 Jul 2009 | 7.2°C22 Jul 1988 | 32 mm8 Jul 1974 | 75 mm1983 · driest 0 mm in 2023 | 52 |
| August | 41.1°C10 Aug 1981 | 7.8°C18 Aug 1973 | 35 mm25 Aug 1977 | 91 mm1977 · driest 0 mm in 2022 | 52 |
| September | 39.4°C2 Sep 1988 | 5.0°C30 Sep 2019 | 46 mm27 Sep 2021 | 174 mm2013 · driest 0 mm in 1993 | 52 |
| October | 33.3°C1 Oct 1987 | -0.6°C30 Oct 1991 | 81 mm27 Oct 1994 | 257 mm2016 · driest 7 mm in 1987 | 52 |
| November | 21.7°C3 Nov 1975 | -7.2°C24 Nov 2010 | 81 mm19 Nov 1996 | 342 mm1973 · driest 29 mm in 1976 | 52 |
| December | 19.4°C10 Dec 1993 | -12.2°C24 Dec 1983 | 78 mm3 Dec 2007 | 473 mm2015 · driest 35 mm in 1976 | 51 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 6 | 6 | <1 |
| February | 0 | 0 | 3 | 4 | <1 |
| March | 0 | 0 | 1 | 4 | <1 |
| April | 2 | <1 | 0 | 3 | 0 |
| May | 6 | 2 | 0 | 2 | 0 |
| June | 9 | 3 | 0 | 1 | 0 |
| July | 20 | 8 | 0 | <1 | 0 |
| August | 21 | 8 | 0 | <1 | 0 |
| September | 12 | 4 | 0 | 1 | 0 |
| October | 1 | 0 | <1 | 3 | 0 |
| November | 0 | 0 | 2 | 6 | 0 |
| December | 0 | 0 | 6 | 7 | <1 |
The best month has moved. On the 1961–1990 numbers the strongest month here was June (scoring 91); on 2011–2025 it is September (94). Both are scored the same way, from the same station — only the climate underneath changed.
| Month | Dry days reaching 20°C | Wet days | Days with heavy rain | Weeks with 3+ wet days | Typical high by year |
|---|---|---|---|---|---|
| January | 0% | 51% | 18% | 64% | 6.0–10.1°C |
| February | <1% | 48% | 14% | 65% | 7.9–12.5°C |
| March | 7% | 49% | 13% | 65% | 11.2–15.6°C |
| April | 21% | 42% | 9% | 56% | 14.3–18.4°C |
| May | 42% | 31% | 6% | 38% | 17.2–21.9°C |
| June | 65% | 21% | 4% | 21% | 21.1–25.2°C |
| July | 89% | 8% | 1% | 4% | 24.3–28.9°C |
| August | 90% | 9% | 2% | 7% | 25.1–28.9°C |
| September | 73% | 18% | 5% | 21% | 21.4–25.7°C |
| October | 25% | 33% | 9% | 45% | 15.8–19.3°C |
| November | <1% | 54% | 19% | 74% | 9.6–13.2°C |
| December | 0% | 53% | 21% | 70% | 5.4–9.5°C |
A dry day reaching 20°C records under 1 mm of rain. A wet day records at least 1 mm, while a heavy-rain day records at least 10 mm. The weekly figure is the share of seven-day periods containing three or more wet days. The final column shows the middle 80% of average daytime highs recorded for that month in individual years; a wider range means conditions have varied more from one year to another.
The evidence behind this page
Where these figures
come from.
- Place identity
- GeoNames 5746545
- NOAA station
- USC00356749 · PORTLAND KGW-TV
- Station distance
- 1.2 km from the place centre
- Climate period
- 1991–2020
- Minimum month coverage
- 29 usable years
- Daylight
- Calculated from latitude 45.52°, mid-month, sunrise to sunset including refraction. Not a station measurement.
- Important limit
- Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.
Next step
Choose your month.
Then plan the details.
The weather comparison for Portland is based on climate evidence, not payments from travel companies. Flight, accommodation and activity links will be clearly labelled when they are added; there are no booking offers on this page today.
How travel partnerships will work