PORTLAND, Ore. (KOIN) — If you’re from the Pacific Northwest, you know that a change is coming to our weather sooner rather than later. Oftentimes it is not just a subtle change — the weather can flip quickly during the fall months.

For Tuesday, we are not only at our average last day for 90 degrees, but we are also at the point of the year where our average high temperature in Portland is now 79 degrees.

What does that mean? It means that our afternoon high temperature should be closer to the upper 70s. We are basically saying goodbye to consistent 80-degree temperatures.

The steady drop of high temperatures the next three months

That may be tough to grasp right now, because we’ve spent most of the end of August in the upper 80s and lower 90s. There have been only one or two signs of cooler temperatures in the last few weeks. You can see from the graphic to the side that we are now in the segment of September that is still warm, and almost prime time weather for the PNW.

You can use that as a cheat sheet for what is to come in the next three to four weeks. Expect a swift transition from the summer heat to the outdoor fall weather.

With all that in mind, we are going to be discussing the last 80-degree days before we know it.

Last year, we didn’t even hit the 90-degree mark in the month of September. We also only had one 70-degree day in the month of October. You should have your fall clothes nearby in the next 20 days.

Average first & last date from 70 to 100 degrees. The average final day of 90 degrees is September 6. The average 80-degree day is September 28.

Portland decided to drop the summer and go straight into fall fairly quickly in 2021. We had our final 80-degree day on September 25. That was an observed high temperature of 85 degrees. One week later, on October 2, we had our final 70-degree day in Portland.

Take advantage of the next month because sometimes we can drop from the 80s to the 60s in just the first month of the school year. However, it doesn’t always work that way.

You can see the list of our final 80-degree days over the last decade in the graphic below. Going back to 2012, our latest 80-degree day was October 15, 2015. On average, going all the way back to the early record keeping at the Portland airport, we usually finish up the 80s around September 27. The latest on record is October 21, 2003.

Now is the time to start planning your favorite early fall hikes around the region.