Best Time to Visit Portland
The best time to visit Portland is June to September, when the average temperature is 15–20°C and rainfall is low for Portland, at 11–57 mm a month.
Portland weather by month
The wettest month in Portland is December with 251 mm of rain, and the warmest is August at an average 20°C. The coolest is December at 3°C.
| Month | Average temperature | Rainfall | Verdict |
|---|---|---|---|
| January | 4°C / 38°F | 216 mm | Wet |
| February | 4°C / 39°F | 144 mm | Cold |
| March | 6°C / 43°F | 178 mm | Wet |
| April | 9°C / 47°F | 119 mm | Cool |
| May | 12°C / 54°F | 79 mm | Cool |
| June | 15°C / 59°F | 55 mm | Best |
| July | 19°C / 66°F | 11 mm | Best |
| August | 20°C / 67°F | 20 mm | Best |
| September | 17°C / 62°F | 57 mm | Best |
| October | 11°C / 52°F | 137 mm | Cool |
| November | 6°C / 43°F | 217 mm | Wet |
| December | 3°C / 38°F | 251 mm | Wet |
How we pick the best months
- Best: an average temperature of 15–28°C and low rainfall for Portland: under 150 mm, and no more than 160 mm, a quarter above Portland's median month (never set below 60 mm).
- If no month qualifies, we show the three driest months that average 10–30°C instead.
- Wet: 150 mm of rain or more. Rainy: more than 160 mm. Hot: 29°C or more on average. Cool: under 15°C. Cold: under 5°C.
Averages cover day and night, so afternoons are warmer than the figure shown. Weather is only one reason to pick a month: school holidays, festivals and prices matter too.
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Where these numbers come from
Monthly averages for January 2001 – December 2020 from the NASA POWER project, for the area around Portland International (PDX) at 45.59, -122.60. The model covers a grid about 50 km across, so a coastal or hilly spot can run a degree or two different. Retrieved 12 September 2026.
The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) Prediction of Worldwide Energy Resource (POWER) Project funded through the NASA Earth Science/Applied Science Program.