May weather forecast
Seattle, WA

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Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington

Weather in May

May, often dubbed "Seattle's secret summer," offers increasingly pleasant weather. There is an increase in daytime temperatures, and the humidity decreases, making conditions ideal for exploring the city’s attractive landscapes and vistas. Longer daylight hours and reduced cloud cover deliver a more significant amount of sunshine, beneficial for both the residents and the thriving flora. The month marks a stark contrast with April, mostly due to the noticeable decrease in rainfall. May’s brisk mornings and warm afternoons perfectly encapsulate Seattle’s charm in spring.

Temperature

The onset of May in Seattle introduces a subtle rise in the average high-temperature, nudging from a mild 56.5°F (13.6°C) in April to an enjoyable 64.8°F (18.2°C). Seattle cools down to an average low-temperature of 44.8°F (7.1°C) throughout the month of May.

Humidity

In May, the average relative humidity is 75%.

Rainfall

In May, in Seattle, the rain falls for 7 days. Throughout May, 0.39" (10mm) of precipitation is accumulated. Throughout the year, in Seattle, there are 84.2 rainfall days, and 5.2" (132mm) of precipitation is accumulated.

Snowfall

April through October and December are months without snowfall in Seattle, Washington.

Ocean temperature

In May, the average ocean temperature is 46.6°F (8.1°C).
Note: Swimming in 46.6°F (8.1°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

Daylight

In May, the average length of the day is 15h and 10min.
On the first day of the month, sunrise is at 5:50 am and sunset at 8:22 pm. On the last day of May, sunrise is at 5:15 am and sunset at 8:58 pm PDT.

Sunshine

In May, the average sunshine is 9.2h.

UV index

The average daily maximum UV index in May in Seattle is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from unsafe exposure to UV radiation for average individuals.
Note: The daily maximum UV index of 4 in May interprets into the following advice:
Act with care - The suggestion to avoid sunburn is emphasized. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. On sunny days, it's ideal to wear sunglasses that filter out UVA and UVB rays.
Updated: Feb 14, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the usual temperature for Seattle in May?

The high-temperature during May is 64.8°F (18.2°C) and the low-temperature is 44.8°F (7.1°C).

What is the average humidity in May in Seattle?

In May, the average relative humidity is 75%.

How many days does it rain in May in Seattle?

In Seattle, Washington, in May, during 7 rainfall days, 0.39" (10mm) of precipitation is typically accumulated.

When it does not snow in Seattle?

April through October and December are months without snowfall in Seattle, Washington.

How cold is the water in May in Seattle?

In Seattle, Washington, the average seawater temperature in May 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.

How many hours of daylight does Seattle have in May?

In May, the average day length is 15h and 10min.

When are sunrise and sunset in May in Seattle?

On the first day of May in Seattle, Washington, sunrise is at 5:50 am and sunset at 8:22 pm. On the last day of the month, sunrise is at 5:15 am and sunset at 8:58 pm PDT.

How many hours of sunshine does Seattle have in May?

In May, the average sunshine duration is 9.2h.

What is the UV index reading in May in Seattle?

In May, the average daily maximum UV index in Seattle is 4. A UV Index of 3 to 5 symbolizes a moderate vulnerability from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in May
Seattle, WA

Average temperature in May - Seattle, WA
  • Average high temperature in May: 64.8°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 (43.7°F).

  • Average low temperature in May: 44.8°F

The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.1°F).

Average pressure in May
Seattle, WA

Average pressure in May - Seattle, WA
  • Average pressure in May: 30.02"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).

Average wind speed in May
Seattle, WA

Average wind speed in May - Seattle, WA
  • Average wind speed in May: 4mph

The windiest month (with the highest average wind speed) is March (5.3mph).
The calmest months (with the lowest average wind speed) are July and August (3.5mph).

Average humidity in May
Seattle, WA

Average humidity in May - Seattle, WA
  • Average humidity in May: 75%

The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).

Average rainfall in May
Seattle, WA

Average rainfall in May - Seattle, WA
  • Average rainfall in May: 0.39"

The wettest month (with the highest rainfall) is December (0.87").
The driest months (with the least rainfall) are July and August (0.12").

Average rainfall days in May
Seattle, WA

Average rainfall days in May - Seattle, WA
  • Average rainfall days in May: 7 days

The month with the highest number of rainy days is November (9.1 days).
The month with the least rainy days is August (2.8 days).

Average snowfall in May
Seattle, WA

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

The month with the highest snowfall is February (0.71").
The months with the least snowfall are April, May, June, July, August, September, October and December (0").

Average snowfall days in May
Seattle, WA

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

The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

Average sea temperature in May
Seattle, WA

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 / Average sunshine in May - Seattle, WA
  • Average daylight in May: 15h and 1min

The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).

  • Average sunshine in May: 9h and 1min

The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).

Average sunshine days in May
Seattle, WA

Average sunshine days in May - Seattle, WA
  • Average sunshine days in May: 20.3 days

The month with the most sunshine days is August (25.9 days).
The month with the least sunshine days is November (16.8 days).

Average UV index in May
Seattle, WA

Average UV index in May - Seattle, WA
  • Average UV index in May: 4

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

Average cloud cover in May
Seattle, WA

Average cloud cover in May - Seattle, WA
  • Average cloud cover in May: 41

The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).

Average visibility in May
Seattle, WA

Average visibility in May - Seattle, WA
  • Average visibility in May: 6mi

The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, November and December (5mi).

Seattle, Washington, USA

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