Triple Digits

When I first arrived in Spokane in the mid-1990s, the climate data at Spokane International showed that the airport averaged one 100F day each year.  But when you looked closer, you would see that only 14 of the 30 years from 1965-1984 had at least one triple-digit day.  In other words, if you're going to hit 100F once in a summer, it's likely you're going to hit it more than once.  Another way to put it is that it was wasn't easy to hit 100F in Spokane.

Recently, this has changed.  And this goes along with my blog a week ago about the recent trend towards hotter summers.  In the most recent 30 years (1995-2024), Spokane has hit 100F forty-two times, or an average of nearly 1.5 times per year.  Hitting triple digits in Spokane is getting to be more common.  In fact, the last summer we had where we didn't have triple digits was the pre-pandemic year of 2019.  We've never had a string of 5 consecutive years of triple digit summers, until now.  In the 1980s, we had 6 consecutive summers without a 100F day.  And in the 1950s, we had 9 such summers.

For this summer, Spokane Airport already has 3 triple digit days.  And if the forecast is right, they'll get three more in the next few days.  That will mean that 3 of the last 4 summers have had six triple digit days.  Prior to that, there had never been more than five 100F days in a summer.

There's something else about the forecast high temperatures for this weekend.  Have you noticed just how high they are?  We're not just talking 101 or 102F.  The forecast for Sunday is now 108F!!!  Just 3 years ago, 108F was the all-time record high for Spokane, which was eclipsed by a degree in late June 2021.  Here's the table of the 10 hottest days in Spokane history (which goes back to 1881).

A quick glance of the table reveals something impressive.  5 of the 10 hottest days in Spokane have occurred in the last ten years.  Even if Spokane comes up a bit short of 108F, hitting 107 or 106 is still extremely rare.

OK, enough about that depressing subject.  What about the expected cooling?  Well, it's still on track to occur next week.  The issue of timing is still with us.  I've shown you this graph before.  The red boxes are the forecast high temperatures.  If the box is narrow, that means all of the computers have good agreement.  The wider the boxes get, the more disagreement there is.  So through Sunday, strong agreement that our highs will be in the triple digits, and not just barely.  108F for Spokane, 106F for Deer Park.  

Then the boxes get a little wider on Monday, but triple digits is again the best bet there.  For Tuesday through Thursday of next week, wide boxes, meaning more uncertainty as the cooler low pressure tries to push into our area.  Eventually it will happen.

Here's our weather map for Sunday.  Hot high pressure over the Pac NW and western Canada.  A cool low in the Gulf of Alaska.

That low will push onshore next week.  Unfortunately, it's going into British Columbia.   The high pressure over the Southwest is just too strong. Previous computer runs had been forecasting the low to come right over us, but they've backed off on that.  We'll still see cooling, but just not as much as what was earlier hoped.  Actually, this pattern will bring rather breezy afternoons.

The good news is that there's decent agreement that the low will sort of stall in this position for several days.  Here's the forecast for next Saturday.  Cool, low pressure over western Canada and the Inland Northwest.  We might actually have a day or two of below-normal temperatures.  (Normal high is 86F at this point).

Looking farther out to the end of the month, we still don't see a return of hot weather to our area.  This is getting pretty far in the future to have much confidence, but for now we can hope.

Through all of this change in the pattern, the chances of rain look very low.  We could be looking at a July without a drop of rain (yes, this has happened before, way back in 1883).

So what does August look like?  The Climate Prediction Center just came out with their update today.  Notice that the highest confidence of heat is now displaced to our east, over the Rockies.  (If you remember some of my blogs during this past spring, this pattern is similar to what the climate models were expecting for our summer).