Tuesday is the start of meteorological fall, but it isn’t going to feel much like autumn across Tennessee next week.
Some of summer’s hottest temperatures appear to be on the way, thanks to an upper level ridge of high pressure that will be parked over the Southeast. The current forecast is for temperatures around 90 degrees each day from Monday through Friday, along with high humidity levels that will drive the heat index to 100 degrees or higher at times.
The same upper level ridge that will deliver the hot temperatures will also keep the region dry, despite the relatively moist air that will be in place. There are slight chances of thunderstorms late in the week, but most of the region will be dry all week.
While the autumn season doesn’t officially begin until the fall equinox on Sept. 22 — the point when daylight and darkness are equal lengths — meteorologists refer to Sept. 1 as the start of autumn. The calendar determines seasons by the equinoxes and solstices, while meteorology keeps things simpler by timing the seasons with the changing of the months, with fall starting Sept. 1, winter starting Dec. 1, spring starting March 1, and summer starting June 1.
Temperatures of 90 degrees or greater aren’t uncommon in September, but they occur less often in September than in July and August. Since National Weather Service records-keeping began in Oneida in the 1950s, the average date of the last 90-degree day of summer is Aug. 27. Temperatures on the Cumberland Plateau peak, on average, in mid-July and slowly decline after that. The decline becomes much more pronounced in mid-September.
Last year, Oneida did not record any 90-degree days in September. There were two in September 2024.
Since 2020, Oneida has had a total of just three days with 90-degree temperatures in the month of September. However, the current pattern — which is being influenced by one of the strongest El Ninos in history — is similar to the one that delivered an extended summer in 2019. That year, the temperature reached at least 90 degrees eight out of nine days between Sept. 10 and Sept. 18, including Oneida’s all-time record for the month of September, 95 degrees, on Sept. 11. That month ended with temperatures more than eight degrees hotter than average.
Summer 2026 has been hot, but not exceptionally so. The month of August will end with temperatures running nearly two degrees above the historic average in Oneida. The same was true for July.
This summer has featured 13 days with 90-degree temperatures so far, which lags behind the 22 days with 90-degree temperatures seen in 2025.
The pattern has also turned exceptionally dry. After the region began the summer season in a drought, excessive rainfall erased the drought status but wet weather has since given way to a return to the abnormally dry conditions that greeted the start of summer. For the year, Scott County is running a rainfall deficit greater than eight inches, receiving about 20 percent less rainfall than it typically would during the months of January through August.
Although streamflows and reservoir levels aren’t low enough for a drought to be declared, decreasing soil moisture levels could impact the fall foliage season, which is about seven weeks from its peak. Fall colors are at their best when the summer is wet, followed by a dry autumn. However, drought or prolonged dry spells that decrease soil moisture can blunt the annual colors.
NOAA’s Climate Prediction Center forecasted above-average rainfall for the Mid-South region during the month of September. However, that forecast appears to be on its way to being proven inaccurate.
For those looking to beat the heat, the Big South Fork National River & Recreation Area’s swimming pool at Bandy Creek Campground will be open Friday, Sept. 4, through Monday, Sept. 7, then close for the season. Admission is $3 for adults or $2 for children. After a summer season that featured mostly above-average streamflows, the recent lack of rainfall has dropped river levels to perfect levels for swimming or wading. Water temperatures are in the low 80s and will slowly rise over the next several days.
