What’s meteorological fall? It’s almost here, with higher temperatures than normal in WA

The final week of August comes with the same rhetoric each year about the end of summer. But the first day of autumn on standard calendars isn’t until September 22.

So, why does the fall rhetoric start in August?

It could be a cultural reference, alluding to the start of the school year and the end of summer break. Or, it could be in keeping with meteorological fall, which differs from the autumnal equinox standard seen on calendars.

In fact, meteorological fall starts on Sept. 1 to make record-keeping easier.

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 September 22 to December 20, with winter beginning on December 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 September 1 and end November 30.

How will the weather be this fall in eastern Washington?

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.

Colby Goatley with the National Weather Service in Pendleton says latest outlooks for fall in the Tri-Cities area are slightly warmer than normal. Somewhere between 2 and 3 degrees is the anticipated increase from Climate Central.

The current predictions for the next week in Tri-Cities show daytime temperatures in the 90s. With such a warm start to meteorological fall, the possibility of above-average fall temperatures is high.

“Going into September, it looks like we’re going to be starting off kind of warmer than normal for meteorological fall,” Goatley told the Herald over the phone. “So it looks like we have a good shot of hitting that warmer overall temperature.”

This story was originally published August 30, 2024 at 5:00 AM.