Portland Weather in May

May brings warm weather to Portland, Oregon and carries on the springtime trend of declining cloud and rain.

This page gives detailed information on the typical May temperature, precipitation, sun, humidity, wind and storms for Portland. The numbers here are historical averages based on climate data gathered near the Portland International Airport, located a few miles from downtown Portland.

Temperature

69 °F	May average high	21 °C
48 °F	May average low	9 °C

13 days	70 °F max. or more (12 °C)
20 days	50 °F min. or less (10 °C)

Most days in May warm to over 60 degrees Fahrenheit (16 degrees Celsius) in Portland. The city averages five days this month when the thermometer reaches into the 80s °F (over 26 °C). Temperatures above 90 °F (32 °C) sometimes occur briefly this time of year.

The thermometer dips to 40 °F (4 °C) or below on an average of 2 nights this month. But May does not normally get cold enough for frost.

Rain

2.8 in	total precipitation	70 mm
14 days	of rain

Half the time, Portland receives 1.7 to 4.0 inches (42 to 102 mm) of rainfall in May. One in four years has drier weather, while another one in four is wetter.

Sun

57 %	sunshine
5 days	clear skies

The sun's rays reach the ground in Portland during 57 percent of daylight hours on average in May, for a total of 264 hours in the month. Typically on 5 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in May at Portland lasts for 14 hours and 55 minutes a day on average. The shortest day of the month is the 1st with 14 hours and 20 minutes of daylight. By the end of the month, the days have lengthened to 15:26 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humidity

69 %	May average humidity

The relative humidity in Portland during May usually peaks at 84 percent in the morning then drops to 52 percent by mid afternoon.

Local Time	1 am	4 am	7 am	10 am	1 pm	4 pm	7 pm	10 pm
Humidity %	80	84	80	66	56	52	60	72

Wind

7.1 mph

May wind speed average

11.4 kph

May is less windy than most other months in Portland.

Storms

2 days	rainfall of 0.5 inches (13 mm) or more
1 day	with thunderstorms in May

A storm that soaks Portland in an inch (25 mm) or more of rain in one day during May happens about once a decade. Portland usually sees more thunderstorms in May than any other month.