Seattle Weather in May

Seattle, Washington enjoys fine weather during May. It's a month of mild temperatures, yet it's sunnier than most months.

This page gives detailed information on the typical May weather for Seattle.

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The temperature, precipitation and sunshine numbers here are historical averages based on climate data gathered at Seattle's Husky Stadium, located near downtown Seattle at the University of Washington on the shore of Lake Washington's Union Bay. The rest of the measurements are averages from the Seattle - Tacoma International Airport, located south of the city center.

Temperature Weather iconTemperature

66 °F May average high 19 °C
49 °F May average low 9 °C

In most years, Seattle averages a daily maximum temperature for May that's between 63 and 68 degrees Fahrenheit (17 to 20 degrees Celsius). The minimum temperature usually falls between 47 and 50 °F (9 to 10 °C).

The days at Seattle warm most quickly during May. By the end of the month, the temperature has climbed around 6 °F (3 °C) above what it was at the start.

9 days 70 °F max. or more (21 °C)
19 days 50 °F min. or less (10 °C)

Usually every day in May the temperature rises to over 50 °F (10 °C) in Seattle. The city averages 1 or 2 days this month when the thermometer reaches into the 80s °F (over 27 °C). Temperatures above 90 °F (32 °C) are not expected here during May.

The thermometer dips to 40 °F (4 °C) or below on an average of 1 night. May does not normally get cold enough for frost.

Rainy Weather iconRain

2.0 in total precipitation 51 mm
12 days of rain

Half the time, Seattle receives 1.2 to 3 inches (31 to 68 mm) of rainfall in May. One in four years has drier weather, while another one in four is wetter.

Sunny Weather iconSun

52 % sunshine
7 days clear skies

The sun's rays reach the ground in Seattle during 52 percent of daylight hours on average in May, for a total of 244 hours in the month. Typically on 7 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in May at Seattle lasts for 15 hours and 9 minutes a day on average. The shortest day of the month is the 1st with 14 hours and 30 minutes of daylight. By the end of the month, the days have lengthened to 15:43 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

69 % May average humidity

The relative humidity in Seattle during May usually peaks at 82 percent in the morning then drops to 54 percent by late afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 78 82 80 68 58 54 61 72

Windy Weather iconWind

8.9 mph May wind speed average 14.3 kph

May is a little windier than most other months in Seattle.

Stormy Weather iconStorms

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

Heavy rainstorms and thunderstorms don't happen every May in Seattle.


These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.

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