This page shows the average precipitation (including snowfall) in each month of the year in Seattle, Washington. It is based on NOAA data for the years 1991–2020., Remarkably, despite being in a region known for its rainfall, the city observes just under nine days of rainfall on average per month, with the highest frequency in November at 9.1 days and the lowest in August at 2.8 days., Analyze Seattle's precipitation patterns and trends from 1978 to present. View monthly and yearly rainfall data, historical precipitation records, and climate change effects on Seattle's weather patterns., Seattle averages 39.34 inches of precipitation a year, with the vast majority falling as rain instead of snow. Official precipitation totals for the city are measured at Sea-Tac Airport, which is actually located south of the Seattle city limits., Rain falls throughout the year in Seattle. The month with the most rain in Seattle is November, with an average rainfall of 7.5 inches. The month with the least rain in Seattle is July, with an average rainfall of 0.7 inches., In an average year, at least 0.01 inches (0.25 mm) of precipitation falls on 150 days, more than nearly all U.S. cities east of the Rocky Mountains. In November, Seattle averages more rainfall than any other U.S. city of more than 250,000 people; it also ranks highly in winter precipitation..