Mercer Island (WA) Monthly Rainfall & Precipitation

This page shows both the average monthly rainfall and the number of rainy days in Mercer Island, Washington State, United States of America. These values are calculated using 30 years of data (1990–2020) to ensure accuracy. Let's explore the details to provide you with a complete overview.

Mercer Island is known for its substantial rain/snowfall, with annual precipitation reaching 1045 mm (41 in). While the overall climate is wet, there are notable seasonal patterns that create interesting contrasts, as demonstrated in our graph below.

Monthly Precipitation Levels

The average number of days each month with precipitation (> 0.2 mm (0.01 in))

The seasons in Mercer Island, bring significant changes in precipitation. The wettest month, November, receives heavy rainfall, with an average of 168 mm (6.6 in) of precipitation. This rainfall is distributed across 21 rainy days.

November, the wettest month, has a maximum daytime temperature of 11°C (52°F). The city receives 73 hours of sunshine in this period. During the driest month July you can expect a temperature of 25°C (77°F). For more detailed insights into the city's temperatures, visit our Mercer Island Temperature page.

Mercer Island's average annual precipitation is 1045 mm (41 in). Let's compare this to some popular worldwide tourist destinations:

In Barcelona, Spain, the average annual precipitation is 620 mm (24 in), evenly distributed across the year with no extreme wet or dry seasons.

Meanwhile, Buenos Aires, Argentina, enjoys a humid subtropical climate with 1000 mm (39 in) of annual rainfall, mostly in the summer.

In Tokyo, Japan, the average annual precipitation is 1528 mm (60 in), with significant summer rains due to typhoon season.

Bangkok, Thailand, experiences a tropical monsoon climate with 1668 mm (66 in) of annual rainfall, with the heaviest precipitation occurring during September and October.

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.

Climate change is affecting precipitation patterns worldwide, including Mercer Island (WA):

• Changing Rainfall Patterns: Global warming causes drastic changes in the patterns of rainfall. Some areas have been experiencing increased frequency and intensity of rainfall, while other areas experience longer dry spells or even droughts.
• Local Impacts: Many regions are experiencing heavier rainfall in the winter months and drier, hotter summers. This affects agriculture, water resources, and ecosystems.

• The U.S. has a significant number of thunderstorms every year, with over 14.6 million taking place across the world annually.
• Approximately 70% of lightning bolts strike land rather than oceans.
• A storm named John was the longest-lasting Pacific tropical storm, continuing for 31 days. As it crossed the dateline twice, it changed status from a hurricane to a typhoon and back to a hurricane.

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