What’s meteorological fall? It’s already here, with temperatures above normal in Olympia

Labor Day is typically seen as the end of summer, even though fall doesn’t technically start until Sept. 22. But meteorological fall doesn’t quite align with astronomical fall, which starts at the autumn equinox. In fact, meteorological fall starts on Sept. 1 to make record-keeping easier. Here’s what to know.

Meteorological vs. astronomical seasons

Astronomical seasons are based on the earth’s position relative to the sun. The first day of fall aligns with the autumnal equinox, and the last day with the winter solstice.

This year, astronomical fall lasts from Sept. 22 to Dec. 20, with winter beginning on Dec. 21.

Conversely, meteorological seasons reflect annual temperature cycles, while aligning with our calendar months.

According to the National Oceanic and Atmospheric Administration, meteorological seasons in the Northern hemisphere are:

• Spring: March, April, May
• Summer: June, July, August
• Fall: September, October, November
• Winter: December, January, February

This means we’re quickly approaching meteorological fall, which will begin Sept. 1 and end Nov. 30.

How will the weather be this fall in Olympia?

Meteorological seasons are often used when conducting research on climate conditions. When examining projections for the upcoming fall across the country, Climate Central found that the planet’s warming trend has continued, and it’s likely the entire U.S. will see temperatures above normal.

According to this recent research from Climate Central, fall has warmed across hundreds of U.S. cities. Temperatures have increased an average of 2.4 degrees Fahrenheit since 1970.

Average fall temperatures in the northwest region have increased 2.7 degrees.

According to the National Weather Service, Olympia will be warmer than usual at the start of September. But after Labor Day weekend, temperatures in Thurston County are expected to cools slightly, according to NWS Seattle meteorologist Samantha Borth.

“We’ll see slight cooling trends Monday and Tuesday but then going into later [in the] week, mid to late, we’ll start to see temperatures increase again. Looking at temperatures back into the 80s, at least Wednesday and Thursday,” Borth said in a phone call with the Olympian.

Here’s NWS’s current forecast for Olympia between Sept. 2 and Sept. 5:

• Monday, Sept. 2 is expected to be partly sunny with a high temperature of 74 degrees
• Sept. 3 is expected to be partly sunny with a high of 74 as well
• Sept. 4 is expected to be sunny with highs approaching 80 degrees
• Sept. 5 is expected to be even hotter, with temperatures approaching 85 degrees

As for the rest of the month, it will likely be more of the same, at least for the first few weeks.

“We’ve got a six to ten day outlook, that looks like it’s going to be trending above normal for western Washington.,” Borth said. “At least the eight to 14 day is looking that way too.”

As September comes to an end, Borth said there’s a better chance that temperatures are at normal levels in Olympia.

“When it comes to weeks three and four, it looks like we’ll get more of an equal chance of being above or below normal,” Borth said.

This story was originally published August 31, 2024 at 5:00 AM.