Why Aren’t Washington Summers Humid?


Well, it turns out the family agreed to come home from Wyoming earlier than expected because we have family coming in from London, England tomorrow and we didn’t want to be rushed to get things in order. So, today was full of indoor and outdoor yard work and the weather couldn’t have been better. I detest yard work, but today it was easier to do it—probably because over the past week I have grown to be very grateful for the summers here.

In Wyoming (and Intermountain West in general) the heat is very warm and dry, making the summer there a true blazing hot summer indeed. It is bearable most of the time, but every once in a while it gets too hot. In the Midwest, the heat there is very warm and humid, often making it feel much hotter than it really is. There are different definitions of “humidity”, but the one I’m talking about is the amount of water vapor in the air.

A common question is: “Why aren’t Washington summers humid if we’re so close to the Pacific Ocean? Wouldn’t that mean greater water content in our air?” Not exactly. It all depends on where we get our heat from. Our warmest days come from an airflow from the north or east which filters in drier air versus the humid air to our west. Once the warm air from the east side gets here it runs down the mountains, compresses and dries out even more, making heatwaves more tolerable here.

Being next to the Pacific Ocean also helps us keep our temperatures from getting TOO hot. Eastern Washington has the Cascades to thank for limiting any major ocean/sea breezes, but here we get them constantly. The main driver of the weather, however, tends to occur from the north and east.

So that is a little bit on why Washington summers—especially Western Washington summers—are typically quite comfortable in comparison to many areas in the country. We average temperatures in the 70s during the summer and we can count on one or two heatwaves (meaning highs in the 90s) every year. Take a look at this Humidity Index (click here) to see how low Seattle’s humidity levels really are compared to the rest of the nation. Typically in the summer we average around 30-40% humidity on a sunny summer day with higher humidity levels on cloudy/drizzly summer days. Not bad!

So when you’re doing yardwork outside, think of the poor folks doing work in 90-100 degree hot/dry weather in Wyoming or the sticky, humid 90-100 degree weather in Missouri. We have it easy here! 🙂

Speaking of which, the next several days look absolutely beautiful here except for tomorrow which looks a bit on the cloudy side. Temperatures will also drop a tad in the upper 60s and lower 70s, but most of next week will be sunny with highs in the mid to upper 70s. Maybe even 80 degrees on Thursday. But models are now being pessimistic for the 4th as it appears clouds and cooler temperatures move on through. We’ll see how that goes…

Have a great evening and enjoy the weather!

Matthew Leach

Forecasting Kitsap




23 thoughts on “Why Aren’t Washington Summers Humid?

  1. have you been here long? Im born and raised here and I can tell you that it is indeed humid in the summer months as well as the rest of the year.

    1. I have lived here my whole life (18 years) and my parents have as well. In comparison to the east coast and midwest, Washington State is not humid at all. We average about 30-40% humidity on a sunny summer day around here which is pretty low. When clouds move in or we have a front roll through, obviously the humidity goes up, but not substantially. Because of the large bodies of water around here we are likely more humid than, say, Idaho or Wyoming, but largely we experience dry heat in the summer. Very rarely do we have a humid day, that is to say humidity levels above 70%.

      In the fall, winter and spring we average 80% humidity, mainly because it is often cloudy/moist/drizzly around here.

      Take a look at the “Humidity Index” (click here) that will tell you the current humidity levels around the nation. Notice how low Seattle’s humidity levels are compared to the midwest, northeast and southeast

  2. Sorry, but the humidity here in Washington is too low to compare to anywhere else in the USA. We do get some muggy days but there’s no mid-west, south or east coast feeling of being hit in the chest by a ton of bricks when going outside.

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