Portland weather in May
In May, Portland has daytime highs averaging 20 °C, nights around 8.9 °C, with 12 wet days. Figures are 1991–2020 climate normals.
- 19.9°C Average high
- 8.9°C Average low
- 12days Wet days
- 72mm Rainfall
- 15h Daylight
Daily temperatures through May
How May develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 May | 18.7 °C | 7.5 °C | 39 % |
| 11–20 May | 19.9 °C | 8.9 °C | 38 % |
| 21–31 May | 20.9 °C | 10.0 °C | 37 % |
- Average highs rise from 18.7 °C early in May to 20.9 °C by the end of it.
What to expect
| Measure | Typical May | Share of the month |
|---|---|---|
| Days above 25 °C | 5.2 of 31 | 17 % |
| Days above 30 °C | 0.6 of 31 | 2 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 12 of 31 | 37 % |
Conditions in May
| Measure | Average |
|---|---|
| Mean temperature | 14 °C |
| Record high (1991–2020) | 34 °C |
| Record low (1991–2020) | 0.9 °C |
| Relative humidity | 73 % |
| Wind speed | 13 km/h |
| Cloud cover | 65 % |
Where Portland ranks in May
| Ranking | Position | Value |
|---|---|---|
| The coolest places in North America in May | 45thof 50 | 20 °C |
May compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| March | 13.1 °C | 146 mm | 74 % |
| April | 15.8 °C | 116 mm | 70 % |
| May | 19.9 °C | 72 mm | 65 % |
| June | 23.0 °C | 46 mm | 58 % |
| July | 28.2 °C | 13 mm | 36 % |
See all twelve months for Portland
- May is the 5th warmest month here.
- It is the 5th driest month of the year.
- It ranks 6th for least cloud cover.
- Days last about 15 hours from sunrise to sunset.
- It rains on 12 of 31 days — 37 % of the month.
- Nights are about 11 °C cooler than the middle of the day.
- The hottest May day on record since 1991 reached 34 °C, 14 °C above the usual daytime high.
Nearby destinations in May
| Destination | Avg high | Wet days |
|---|---|---|
| Portland | 20 °C | 12 |
| Vancouver | 20 °C | 13 |
| Salem | 20 °C | 9 |
| Eugene | 19 °C | 11 |
| Tacoma | 18 °C | 11 |
QuestionsMay in Portland, answered
How warm is Portland in May?
Daily highs average 20 °C and nights fall to about 8.9 °C, a spread of 11 °C between afternoon and dawn. That makes May the 5th warmest month of the year here.
Does it rain much in Portland in May?
May averages 72 mm of rain, spread over about 12 of the 31 days — 37 % of the month. Cloud cover averages 65 % of the sky.
How long are the days in May?
Portland averages 15 hours between sunrise and sunset in May. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.