Is Seattle Humid? (Yes, but it’s not what you think…)

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I was in Phoenix on vacation recently and I went to Target to get some cough medicine for a sick friend. As I showed the cashier my driver’s license, he said, “What’s the weather like up there? Do you get a lot of humidity?”

I paused for a second and thought, “Humidity? Seattle?” It’s not the first word would use to describe our climate. I was also really tired at the time and, thankfully, one of my friends saw that I was having trouble and he stepped up to answer.

Do you know if Seattle is humid? First, let’s look at what we mean by “humidity” and then we’ll see if the term applies to Seattle’s climate.

What is Humidity?

Most people are aware of the concept of humidity but couldn’t give you an exact definition if you asked, based on the informal poll I did of my other friends once I got back to town.

Humidity refers to the amount of water vapor in the air around us. In the same vein, a humidifier is a device that makes the air more “moist” and a dehumidifier does the opposite by removing those gaseous water particles.

There are several several types of humidity, including “absolute“, which is an actual measure of the density of water molecules in the air.

However, for this discussion, we’re specifically referring to “relative humidity“, which refers to the amount of water vapor in the air relative to what you’d expect based on the current temperature.

For example, if the air in your home seems hotter than the thermostat would suggest it should be, it usually means the humidity is too high. On the other hand, if you have dry skin and an irritated nose, the humidity could be too low.

Another interesting fact is that it is generally more humid indoors than it is outside. The main cause for this is that air conditioning systems blow cool air into the building which tends to have more moisture and is being blown into an enclosed space.

Speaking of Phoenix, you’re probably familiar with the expression “it’s a dry heat,” which suggests that Arizona’s lack of humidity makes the heat more bearable. It’s kind of a myth because it gets quite humid during monsoon season, but you get the idea.

Is Seattle Humid?

Just for fun, I asked a few people once I got back into town if they thought Seattle had a lot of humidity. Most of them laughed and said no, a few asked me to clarify what humidity actually means, and I got at least two responses of “I don’t know.”

This may surprise you but according to several studies, Seattle is in the top 50 most humid cities in the United States. Of cities with a population of one million people or more, it’s in the top ten.

That being said, it doesn’t really feel humid most of the time, especially if you’ve recently been to a place with more pronounced humidity like Utah, Arizona, or even parts of Alaska. People who have lived here for years often don’t even notice it.

There’s a simple explanation for this which relates to Seattle’s geography. Because the city is located on Puget Sound, which is an inlet of the Pacific Ocean, there’s a lot of water nearby.

Those waters draw a lot of heat, which then changes into a gaseous state and becomes water vapor. Since high amounts of water vapor in the air is the very definition of humidity, it makes sense that Seattle would be one of the highest in the country.

However, the reason it doesn’t feel overly humid here is that the mountains that surround Seattle help provide a more temperate climate by changing the way air reaches the city.

Some Statistics on Humidity in Seattle

In the summer months, the average humidity in Seattle is about 66%. In winter, that number gets closer to 80%.

For reference, experts say that the range of comfortable humidity will vary from person to person but the upper limit is usually between 55% and 60%. This puts Seattle in the “high” range year-round.

If you want to experience Seattle’s humidity at its highest point, go outside at night when it’s higher. According to Bing Weather, just past midnight on the day I’m writing this, it’s expected to get as high as 91% tonight!

This is actually the case everywhere because it’s colder after the sun goes down. There’s less heat to soak up some of the moisture in the air and therefore, it’s more humid. That’s also why the average is higher in winter than it is in the summer.

Final Thoughts

To sum up, yes, Seattle is very humid! However, the city’s location and geography both cause the humidity and prevent it from being too noticeable or unpleasant. Sure, it gets a little cold sometimes but I’ll take our humidity over Houston’s 99 times out of 99.

Living in Seattle definitely isn’t perfect and there are a lot of things that I don’t love about it sometimes. However, the humidity is definitely not on that list.

If you’re planning a trip to the Pacific Northwest, you should be prepared for a little extra humidity by staying hydrated, especially if you have a medical condition that can be affected by extra moisture in the air.

As long as you take a few precautions and are mindful of the humidity, you’ll be sure to have a great time on your next vacation or business trip to beautiful Seattle. We can’t wait to see you soon!