Weather Blog

September -- the forgotten 4th month of Seattle's '3-month' summer

September -- the forgotten 4th month of Seattle's '3-month' summer

September seems to get a bad rap around here. We all talk about how Labor Day is the unofficial end to summer, school vacation is ending, and heck, even fall begins during this month.

Meanwhile, June gets lumped in with summer stalwarts July and August. And why not? Summer begins in June, we're starting to come off our rainy and chilly spring, and kids are champing at the bit to burst away from their classrooms.

You know the phrase: "Seattle, it rained 9 months of the year there, right?" -- ask anyone what the three months are that it doesn't rain and they'd likely say June, July and August.

Maybe it's also because the transition from summer to fall is very quick in Seattle -- we're just four weeks away from October and the official start to the rainy season, whereas the transition from spring to summer is more gradual. In June, you look at a half sunny day and you'd probably say it was partly sunny. Look at the same day now in September, and it's likely "mostly cloudy."

But believe it or not, September has quite a weather resume in Seattle. And dare I say, it's a little more impressive than June. After all, June only has 9 official days of summer while September has 21!

September averages 1.50" of rain in the month -- drier than June's 1.57 inches. September's average high is 70.5 degrees. June? 69.9.

While both months average nine days of measurable rain in the month, in September, you have a slightly better chance of remaining dry on any given date: 27.1% chance of getting measurable rain on a day versus 29.5% in June.

With the marine layer much more of a factor in the early summer, June averages 17 overcast days in the month, while September has 13. On the other hand, September is considerably foggier than June -- an average of 5 days with dense fog compared to just under 1 day on average for June.

Now, one area where June does have an advantage is getting heat waves. There have been 28 June dates where the temperature has reached 90 or hotter, compared to just 10 in September (although ask me again after next week if it's still 10.)

Or... maybe it should just be declared a tie. Over the past 10 years, it's an even split -- four years where June was hotter than September, four years the other way, and two years it was a tie.

But overall, if you had to pick one or the other to be our "third month", maybe it should be September?

Or, maybe we just get the word out that it really only rains eight months of the year here :)