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May Weather in Portland, United States

Last updated: June 24, 2025

In Portland, United States, the average temperature in May hovers around 15°C (60°F), with minimums dipping to 1°C (35°F) and maximums soaring to 33°C (92°F). Expect around 111 mm (4.4 in) of precipitation spread over 12 days, contributing to an average humidity of 69%. Stay prepared for varying weather conditions!

May Temperature in Portland

In May in Portland, the average temperature is 15°C (60°F). Maximum temperatures can reach 33°C (92°F), while minimums can drop as low as 1°C (35°F). Be sure to pack layers to accommodate the wide range of temperatures during your travels.

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 15°C (60°F), with highs reaching up to 33°C (92°F) and lows dropping to around 1°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec323439495969757467574436
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) over a span of 12 days.

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 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec67909012611194156969913090127
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 69%. With an average temperature of 15°C (60°F), this humidity feels like a cool, damp embrace that can make outdoor activities feel slightly heavier and more exhausting, but still inviting for exploring the charming sights and sounds of the area.

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 69%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%81%78%70%69%62%65%68%74%82%80%
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 reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec35681010998642
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 Weather0°C (32°F)67 mm (2.6 inches)84%moderate
February Weather1°C (34°F)89 mm (3.5 inches)82%moderate
March Weather4°C (40°F)90 mm (3.6 inches)81%high
April Weather10°C (49°F)126 mm (5.0 inches)78%very high
May Weather15°C (60°F)111 mm (4.4 inches)69%very high
June Weather20°C (69°F)94 mm (3.7 inches)69%very high
July Weather24°C (75°F)156 mm (6.1 inches)62%very high
August Weather23°C (74°F)96 mm (3.8 inches)65%very high
September Weather20°C (67°F)99 mm (3.9 inches)68%very high
October Weather14°C (58°F)130 mm (5.1 inches)74%high
November Weather7°C (44°F)90 mm (3.6 inches)82%moderate
December Weather2°C (36°F)127 mm (5.0 inches)80%low

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