May weather forecast and climate
Seattle, WA

Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
May is the loveliest month in Seattle as the days begin to become longer than nights. Temperatures rise to a moderately warm range of 46.4°F (8°C) to 64.4°F (18°C), and humidity drops to a tolerable 68.3% making this the best weather across the year.
Rain only falls for eleven days, and the rain gauge meters read 2.1" (53.3mm), making it easier to tour Seattle without interruptions. Packing an emergency rain jacket is necessary.
The sea warms up to a moderately lovely 53.6°F (12°C), and the eight hours of sunshine make swimming worthwhile.

What is the temperature in May in Seattle?

In May, in Seattle, the average high-temperature is 64.8°F (18.2°C), and the average low-temperature is 47.3°F (8.5°C).

How much does it rain in Seattle in May?

In Seattle, during May, the rain falls for 12 days and regularly aggregates up to 1.9" (49.3mm) of precipitation.

What is the sea water temperature in May in Seattle?

In May, in Seattle, Washington, the average sea temperature is 46.6°F (8.1°C). Swimming in 46.6°F (8.1°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.
Average temperature in May - Seattle, WA
  • Average high temperature in May: 64.7°F

The warmest month (with the highest average high temperature) is August (76.3°F).
The month with the lowest average high temperature is December (45.7°F).

  • Average low temperature in May: 47.3°F

The month with the highest average low temperature is August (55.9°F).
The coldest month (with the lowest average low temperature) is December (35.6°F).

Average humidity in May - Seattle, WA
  • Average humidity in May: 68.9%

The month with the highest relative humidity is December (80.1%).
The month with the lowest relative humidity is July (65.4%).

Average rainfall in May - Seattle, WA
  • Average rainfall in May: 1.9"

The wettest month (with the highest rainfall) is November (6.6").
The driest month (with the lowest rainfall) is July (0.7").

Average rainfall days in May - Seattle, WA
  • Average rainfall days in May: 12 days

The month with the highest number of rainy days is November (18.4 days).
The month with the lowest number of rainy days is August (4.8 days).

Average snowfall in May - Seattle, WA
  • Average snowfall in May: 0"

Months with the highest snowfall are February and December (1.7").
Months with the lowest snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in May - Seattle, WA
  • Average snowfall days in May: 0 days

The month with the highest number of snowfall days is December (1.6 days).
Months with the lowest number of snowfall days are April, May, June, July, August, September and October (0 days).

Average sea temperature in May - Seattle, WA
  • Average sea temperature in May: 46.6°F

The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is February (45.3°F).

Average daylight in May / Average sunshine in May - Seattle, WA
  • Average daylight in May: 15.2h

The month with the longest days is June (Average daylight: 15.9h).
The month with shortest days is December (Average daylight: 8.5h).

  • Average sunshine in May: 8.2h

The month with most sunshine is July (Average sunshine: 10.1h).
The month with least sunshine is December (Average sunshine: 1.7h).

Average UV index in May - Seattle, WA
  • Average UV index in May: 6

Months with the highest UV index are June and July (UV index 7).
Months with the lowest UV index are January, November and December (UV index 1).

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