Hottest Day of the Summer next week

The title of today's blog may sound a bit presumptuous.  After all, summer isn't over yet.  Let me show you why I'm pretty confident that next Tuesday will be the hottest day of this summer.

Currently, cooler weather is winning the battle across the lower 48 states, including the Northwest.  But you'll notice a slight hint of a warm high pressure ridge developing off the WA/OR coast (red shading).

By tomorrow afternoon, a strong area of high pressure has quickly developed in our neck of the woods.  This will cause temperatures to warm rapidly over the next few days.

The peak of the heat looks to be on Tuesday, when the high pressure is at its strongest, with the center just off shore.

This is a hot weather pattern.  But it's not connected to a 4-corners high.  Those tend to be long-lived heat waves (10-14 days).  Rather, this pattern looks rather similar to the heat wave of 2021.  Thankfully, we're not expecting to get that hot.  Also, this is a hot pattern for those folks west of the Cascades.  Folks in Portland and Eugene and even on the coast will be feeling it by Sunday.  Here's the Monday high temperature forecast from one model:

As is usually the case, the west side will start to cool down on our hottest day, which will probably be Tuesday.  Triple digits are likely in some areas, possible in others.

But after Tuesday, high pressure will begin to weaken and temperatures will gradually cool.  By the end of next week, the heat will be over.  In fact, we will have normal temperatures through at least the 21st, and possibly longer.  Here's the forecast for Saturday the 19th.  A cool trough has replaced the hot ridge along the west coast, while the heat is on for the central US.

So couldn't we see still see even hotter weather before Labor Day?  It's possible, but rare.  Let's assume that Spokane airport hits 100F or higher next Tuesday (or maybe Wednesday).  The expected cooling after that will remove 100F from the forecast at least until after the 21st.  Spokane has never reached 100F in September, and only 4 times has it done it in the last third of August.  Days are getting shorter.

But here's the catch.  One of the 4 times that Spokane reached 100F in the waning days of August was......last year.  Yep, just a year ago Spokane hit 100F on the last day of August, tying it for the latest 100F ever.  So can't that happen again this year?  Yes, but the odds are in my favor (4 times in 141 years), and I'll take those odds.  So if you're a fan of triple digits, be sure to enjoy next week.

Here's a temperature and dew point forecast graph for Deer Park that shows you what we've been discussing.  

A couple of notes.  Aside from the high temperatures reaching the 90s for the period Sunday through Friday, min temperatures are going to be interesting.  For the first half of the hot spell, skies will be clear and winds light at night.  So we'll still be cooling into the lower 50s.  Good for sleeping and cooling off the house.  The dew points will be in the 40s, so morning dew will be hard to come by if you're trying to bale some 2nd cutting alfalfa.  There was a light dew this morning, but it may be the last one for awhile.  But dew points shouldn't crater into the 30s so morning humidity will still be decent, probably around 70%.

After the hottest day on Tuesday, winds will get a little breezier during the day.  Since this is a slow cool down, I don't expect a really windy day.  (The amount of wind is usually proportional to the amount of cooling).  But the wind could be enough to keep nighttime temperatures a bit warmer for the rest of the week.