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May Weather in Portland, United States

Last updated: June 24, 2025

In May, the average temperature in Portland, United States hovers around 11°C (52°F), with minimums dipping to 0°C (32°F) and reaching maximums of 22°C (72°F). Expect 111 mm (4.4 in) of precipitation spread over 14 days, contributing to an average humidity of 82%.

May Temperature in Portland

In May in Portland, the average temperature is a mild 11°C (52°F). Maximum temperatures can reach a pleasant 22°C (72°F), while the minimum can dip as low as 0°C (32°F). This climate makes Portland an ideal destination for travelers seeking a comfortable and varied weather experience.

May Weather in Portland: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in Portland, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Portland, May typically has an average temperature of 11°C (52°F), with highs reaching up to 22°C (72°F) and lows dropping to around 0°C (32°F).
JanFebMarAprMayJunJulAugSepOctNovDec292934415163717166564235
Data source: Temperature data for Portland generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

May Precipitation in Portland

In Portland in May, the precipitation amount is 111 mm (4.4 in) during 14 days, indicating a significant amount of rainfall for that period.

May Precipitation Trends in Portland

The chart displays monthly precipitation patterns in Portland, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Portland, May typically receives around 111 mm (4.4 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec9898951121111021268588151125128
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Portland

In Portland in May, humidity is 82%. With an average temperature of 11°C (52°F), this humidity feels like a damp chill that seeps into your bones, making it essential to dress in layers and stay prepared for the moisture-laden air as you explore your surroundings.

May Average Humidity in Portland

This chart illustrates the average monthly humidity levels in Portland, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Portland is approximately 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec91%91%88%88%82%80%77%72%76%83%88%87%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Portland

In Portland in May, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Portland.

Maximum UV Index Levels in Portland for May

The chart shows the monthly maximum UV Index (UVI) for Portland in May, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In May, the maximum UV index in Portland typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec24689101098642
Data source: Portland May UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How May Weather in Portland Compares to Other Months

Weather in Portland varies notably across the year, with each month offering distinct climate conditions. This page compares May’s weather to other months in Portland, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Portland, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (29°F)98 mm (3.9 inches)91%low
February Weather-1°C (30°F)98 mm (3.9 inches)91%moderate
March Weather1°C (34°F)95 mm (3.7 inches)88%high
April Weather5°C (41°F)112 mm (4.4 inches)88%very high
May Weather11°C (52°F)111 mm (4.4 inches)82%very high
June Weather17°C (63°F)102 mm (4.0 inches)79%very high
July Weather22°C (72°F)125 mm (4.9 inches)77%very high
August Weather22°C (71°F)85 mm (3.3 inches)72%very high
September Weather19°C (66°F)88 mm (3.5 inches)76%very high
October Weather13°C (56°F)151 mm (5.9 inches)83%high
November Weather6°C (43°F)125 mm (4.9 inches)88%moderate
December Weather2°C (36°F)128 mm (5.0 inches)87%low

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