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 temperature, precipitation, sun, humidity, wind and storms for Seattle. The weather measurements are averages based on climate data gathered at Seattle — Tacoma International Airport, located south of the city center.
Temperature
| 66 °F | May average high | 19 °C |
| 49 °F | May average low | 9 °C |
| 8 days | 70 °F max. or more (21 °C) |
| 22 days | 50 °F min. or less (10 °C) |
Usually every day in May the temperature rises to over 50 degrees Fahrenheit (10 degrees Celsius) in Seattle. The city averages 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.
Rain
| 1.9 in | total precipitation | 48 mm |
| 11 days | of rain |
Half the time, Seattle receives 1.1 to 2.8 inches (29 to 70 mm) of rainfall in May. One in four years has drier weather, while another one in four is wetter.
Sun
| 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.
Humidity
| 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 Time | 1 am | 4 am | 7 am | 10 am | 1 pm | 4 pm | 7 pm | 10 pm |
| Humidity % | 78 | 82 | 80 | 68 | 58 | 54 | 61 | 72 |
Wind
| 8.9 mph | May wind speed average | 14.3 kph |
May is a little windier than most other months in Seattle.
Storms
| 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.
Reference
The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.