When I moved to Seattle 20 years ago, I remember everybody saying the same thing about air conditioning: “Why bother? It only gets really hot a couple times a year.”

That perception, I would say, no longer exists. Very hot days seem a lot more common, and people often chalk it up to climate change. But does the data bear this out?

I looked at the National Weather Service data for the number of days each year when the high temperature at Sea-Tac hit 90 degrees or higher, going back to 1945 when the record-keeping began.

And the answer is yes. Recent years have had an unusually high number of very hot days.

Seattle heat wave likely to be longer, hotter than expected

In total, there were 246 90-plus-degree days in Seattle from 1945 through June 2022. One hundred of those days have occurred in the past 20 years.


Since 1945, there were only nine years when we’ve had seven or more 90-plus-degree days in Seattle, and five of those nine years have been since 2015.

In fact, 2015 had the most days, clocking in at 12, on record, when the thermometer spiked into the 90s or 100s. The year with the second-most such days was 2018, at 11. Both 2021 and 2017 had eight, and in 2016, there were seven.

2021, of course, included that record-breaking 108-degree day on June 28.

Since 2015, the only years that were more like “normal” for Seattle were 2020, with four very hot days, and 2019, with only two.

We are in a heat wave now, so we’ll see how many we rack up for 2022, but it seems like a safe bet to say there will be more than seven once again.

If you’re among the tens of thousands who moved to the Seattle area in the past decade, you won’t recall a single summer without a 90-plus-degree day. The last time that happened was 2011.

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Maybe years like that are no more, but they weren’t all that rare in the past. Since 1945, there have been 16 years with zero very hot days — zero times when people needed tips on staying cool, like freezing your pillowcase. In the three-year stretch from 1999-2001, the temperature never hit 90 degrees in Seattle.

And in the 10 years from 1945 to 1955, half of those years never got up to 90 degrees. Sounds nice, huh?

It’s because of our history of mild summers that Seattle has been — and remains — the least air-conditioned large metro area in the country. The most recent data from the Census Bureau’s American Housing Survey shows less than half, 44%, of homes in our metro area had air conditioning in 2019.

Many Seattleites may be starting to feel like air conditioning is no longer optional, as data reveals a big jump in the share of air-conditioned homes in a short period. The 2013 American Housing Survey showed less than one-third, 31%, of homes here had air conditioning.

All that said, it’s not like there were never hot summers in the past. What may be common now has happened before, but it happened less frequently than what we’ve seen over the past decade. The most notable example is 1958, when there were nine 90-plus-degree days, the third most on record.