The last heat wave of summer? When does the threat go away?

Even as temperatures cool this weekend, the specter of more warmth is on the horizon.

But is this the end of the real warming threat in our region?

Let’s start with the forecast. Another high pressure peak will build on the West Coast on Monday and Tuesday, as illustrated by the upper level map (500 hPa pressure, about 18,000 ft) at 5 p.m. Tuesday. Red indicates higher than normal pressure, blue and purple below normal (rough.

The National Blend of Models’ latest temperature forecast for Seattle shows 80s highs on Tuesday and Wednesday before cool weather extends to higher seasonal temperatures. about 80F. Crucially, the lows will reliably drop into the 50s, ensuring you’ll get a good night’s sleep.

As you all see clearly, the nights are getting longer, the days are getting shorter and the strength of the sun’s rays are dwindling. In the end, we simply won’t be able to enter the 80s and 90s anymore.

But when? What does climatology tell us?

To support this analysis, let’s look at the climate of temperatures on both sides of the Cascades in late summer and early fall (August 1 to November 15, see below). Each chart below shows record highs (red) and lows (cyan) and average high/low ranges (brown). I also graphed this year’s temperatures (blue bars) and noted the 80, 90, and 100 F levels with the dashed lines.

For SeaTac Airport, temperatures were higher than 90 degrees Fahrenheit several times in August and early September, but never after October 1. Highs above 80 degrees Fahrenheit occurred until mid-October.

Bottom line, the threat of temperatures above 90 degrees Fahrenheit in western Washington should be gone in a month, with little chance of temperatures exceeding 95 degrees Fahrenheit after September 1.

For the Tri-Cities (Pasco shown below), getting above 100F wasn’t a big deal in August, but became unprecedented after the first week of September. The turn to the 90s happened. several times in September, but becomes unprecedented in October. October is a very crowded month in Washington.

The bottom line: Based on current projections, it looks like after midweek, there’s probably little chance of Seattle breaking 90F for the rest of the year. And after Friday, it’s very unlikely that Richland will exceed 100F for the rest of 2022.

Reminder: I will be teaching Atmospheric Science at ATMS 101 this fall.

Like last year, I’m teaching atmospheric science 101: a general introduction to weather and climate, this fall. You can learn more about the class on class website. I talk about everything from atmosphere basics to weather prediction, thunderstorms, storms, and local weather to climate and global warming.

I will be teaching the class in person at UW, but will also be delivering it via zoom. So people can get it remotely.

Have you been moderated by The Seattle Times?

I’ve noticed a serious problem at the Seattle Times: they censor people who leave comments with different views on climate change with their actions based on allegations of “climate misinformation.” . If you have been censored by the Seattle Times, including removing your comments or locking your account, please let me know by email or as a comment on this blog (I will not reveal your identity).

This is a very serious matter and reflects a disturbing attitude at our local newspaper.