May Weather in Washington, United States

Last updated: June 24, 2025

In May, the average temperature in Washington, United States is a pleasant 18°C (65°F), with temperatures ranging from a cool 3°C (37°F) to a warm 37°C (99°F). Expect around 201 mm (7.9 in) of precipitation over the course of 14 days, contributing to an average humidity level of 82%. This combination of warmth and moisture creates a vibrant and lush atmosphere throughout the month!

May Temperature in Washington

In May in Washington, the average temperature is 18°C (65°F). Maximums can reach up to 37°C (99°F), while minimums can drop as low as 3°C (37°F). Travelers should be prepared for a wide range of temperatures, so layering clothing is advisable.

May Weather in Washington: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in Washington, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Washington, May typically has an average temperature of 18°C (65°F), with highs reaching up to 37°C (99°F) and lows dropping to around 3°C (37°F).

Data source: Temperature data for Washington generated using information from the Copernicus Climate Change Service.

May Precipitation in Washington

In Washington in May, the precipitation amount is 201 mm (7.9 in) over a span of 14 days.

May Precipitation Trends in Washington

The chart displays monthly precipitation patterns in Washington, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Washington, May typically receives around 201 mm (7.9 inches) of precipitation spread over approximately 14 days.

Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

May Humidity in Washington

In Washington in May, humidity is 82%. With an average temperature of 18°C (65°F), this humidity feels like a warm, sticky embrace that can quickly leave travelers feeling fatigued and in need of frequent breaks to stay refreshed and hydrated.

May Average Humidity in Washington

This chart illustrates the average monthly humidity levels in Washington, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Washington is approximately 82%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Washington

In Washington in May, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Washington.

Maximum UV Index Levels in Washington for May

The chart shows the monthly maximum UV Index (UVI) for Washington in May, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In May, the maximum UV index in Washington typically reaches 10, which falls under the very high exposure category.

Data source: Washington May UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How May Weather in Washington Compares to Other Months

Weather in Washington varies notably across the year, with each month offering distinct climate conditions. This page compares May’s weather to other months in Washington, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Washington, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-1°C (30°F)	28 mm (1.1 inches)	76%	moderate
February Weather	-1°C (30°F)	27 mm (1.1 inches)	77%	moderate
March Weather	7°C (45°F)	86 mm (3.4 inches)	70%	high
April Weather	12°C (53°F)	60 mm (2.4 inches)	73%	very high
May Weather	18°C (65°F)	201 mm (7.9 inches)	82%	very high
June Weather	25°C (78°F)	94 mm (3.7 inches)	82%	extreme
July Weather	27°C (81°F)	89 mm (3.5 inches)	81%	extreme
August Weather	25°C (77°F)	95 mm (3.7 inches)	78%	very high
September Weather	22°C (72°F)	67 mm (2.7 inches)	71%	very high
October Weather	13°C (55°F)	121 mm (4.8 inches)	71%	high
November Weather	6°C (43°F)	31 mm (1.2 inches)	81%	moderate
December Weather	2°C (35°F)	28 mm (1.1 inches)	84%	moderate