Seattle (WA) Rainfall & Precipitation: Monthly Averages and Year-Round Insights

This page shows the average amount of rainfall per month in Seattle (WA). The numbers are calculated over a 30-year period to provide a reliable average. Let’s explore the details in depth to provide you with a complete overview.

Seattle has a notably wet climate with abundant precipitation, recording 1009 mm of rain/snowfall per year.

Monthly Precipitation Levels

The average number of days each month with precipitation (> 0.2 mm)

Seattle can be quite wet during November, receiving approximately 166 mm of precipitation over 20 rainy days.

In contrast July, experiences much drier conditions, with 14 mm of rainfall, spread across 4 rainy days.

November, the city’s wettest month, has a maximum daytime temperature of 11°C. During the driest month July you can expect a temperature of 25°C. For more detailed insights into the city’s temperatures, visit our Seattle Temperature page.

Annual Precipitation in the United States of America

The map below shows the annual precipitation across the United States of America. You can also select the different months in case you are interested in a specific month.

Amsterdam Precipitation Compared World Wide

Seattle’s average annual precipitation is 1009 mm. Let’s compare this to some popular worldwide tourist destinations:

Boston, USA, experiences 1238 mm of annual precipitation, including significant snowfall during the winter.

In Shanghai, China, the annual average precipitation is 1347 mm, with a humid subtropical climate.

Perth, Australia, receives 565 mm of rainfall annually, mostly during the winter months.

Ho Chi Minh City, Vietnam, receives 1955 mm of annual rainfall, with a pronounced wet season from May to November, typical of its tropical monsoon climate.

How is Precipitation Measured?

Precipitation amounts are measured using specific gauges installed at weather stations, collecting both rain and snow and any other type of precipitation. Rainfall is measured directly in millimeters, while that from snow and ice is obtained by melting it. Automated systems often incorporate heaters to make this easier.

Information from these stations is transmitted via Wi-Fi, satellite, GPS, or telephone connections to central monitoring networks. This information is immediately updated and integrated into weather models and forecasts.

Global Precipitation Patterns

Tropical Rainforests: In tropical regions, rainfall is generally abundant year-round. Areas near the equator, like the Amazon rainforest, can receive up to 3000 mm of rain annually.

Desert Regions: Deserts such as the Sahara and Arabian deserts typically see less than 250 mm of rainfall annually. Rainfall tends to be infrequent, but when it does occur, it is often intense.

Temperate Zones: In temperate regions, precipitation tends to be more evenly distributed, though areas closer to the ocean may see more rain in the winter months, and areas further inland experience drier summers.

Polar Regions: Precipitation in polar regions, like Antarctica, is extremely low, often falling as snow. Average annual precipitation in Antarctica is less than 200 mm, with some areas receiving as little as 50 mm annually.

For more detailed information about Seattle (WA)’s weather, including sunshine hours, humidity levels, and temperature data, visit our Seattle (WA) Climate page.