Mercer Island weather in September (Washington State, United States of America)

How does the September weather in Mercer Island compare to other months? Thinking about a visit? Explore this page for a full overview of the weather conditions this month.

Temperatures

Expect perfect weather in Mercer Island during September, which means pleasant temperatures and moderate rainfall. Enjoy the summer season during this month. The temperature during the day can rise to approximately 22°C. At night, it falls to around 12°C.

Precipitation

Mercer Island in September usually receives moderate rainfall, averaging around 52 mm for the month. Rain is expected on roughly 10 days.

Average sunshine

Expect a lot of sunshine this month, with about 220 hours of sunny weather. The abundant sunlight creates a lively and bright atmosphere.

So this is a great month to visit if you prefer dry days with pleasant temperatures. June, July, August and September typically offer the most optimal weather. In contrast, January, February, March, November and December tend to have less optimal conditions.

For an in-depth look at the yearly conditions, visit our specialized Mercer Island climate page with graphs.

 

Mercer Island, monthly averages in September

Min Temperature 12°C  

Max Temperature 22°C  

Chance of Rain 33%  

Precipitation 52 mm  

Rainy days 10 days  

Humidity 73% *  

Windspeed 14 km/h *  

Sunshine 220 hours *  

Percentage Sunshine 59% *  

Data from: Seattle, the United States of America (15 KM, 9 Miles).

Where to go in the United States of America in September

Find out more about the weather in the United States of America and which places have the best travel conditions in this month.

Weather conditions Weather

Temperatures

Precipitation

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Legend perfect weather pleasant tolerable unpleasant poor

Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C and 29°C and not too much precipitation (less than 90 mm a month).

So, what should you wear in this month?

For visitors traveling to Mercer Island, we recommend wearing layers. So maybe a skirt, t-shirt, shorts for during the day and jeans and a warm jacket for some days and evenings. Bring a rain jacket in case it rains during your stay. Plan on layering your clothes.

What To Do

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Cycling

10/10

Walking

10/10

Barbeque

9/10

Camping

8/10

Outdoor sports

10/10

Interested in more climate information?

This site provides you with all the information you need about the climate in Mercer Island.

Our site offers climate and forecast data for every country in the world. Are you going to the United States of America? On this website you can find historical weather averages for many cities in the United States of America. Not sure yet where to go? We now have a tool which recommends destinations that suit your ideal travel conditions. Find out where to go with our weather planner.