A burst of late-September heat in Tennessee came with an unusual distinction: weather creator @ryanhallyall said the state was under the strongest heat dome anywhere on Earth, a setup that helped push temperatures into extreme territory.
Here's what to know
In a TikTok video, Hall pointed to the state's atmospheric midpoint, saying it stood at 19,665 feet above sea level — a level he said was higher than anywhere else on Earth as the hot air mass swelled overhead.
@ryanhallyall The strongest heat dome on the planet right now is sitting over Tennessee. Not the Sahara. Not the Middle East. Tennessee. Heat makes air swell. Over Tennessee the halfway point of the atmosphere is 19,665 feet up, higher than anywhere else on Earth. Nashville hit 100 on September 15. In 153 years of records it has only been this hot this late one other time. The dome starts shifting this weekend. I'll tell you when a cold front finally breaks it.
♬ original sound - Ryan Hall
According to Hall, Tennessee was sitting beneath a major heat dome, the kind of pattern that acts like a lid and lets heat accumulate. He said the air under a large dome sinks instead of rising, and as it descends it becomes warmer and drier, making cloud formation less likely and allowing temperatures to continue climbing.
Memphis climbed to 100 and set a daily record, while Nashville reached 100 degrees on Sept. 15 — a level of late-season heat that has occurred only once before in 153 years of records.
He said Chattanooga was caught in the same prolonged stretch, with temperatures above 90 degrees for 43 straight days, the longest such streak ever recorded there.
"Not the Sahara. Not the Middle East. Tennessee," Hall said, emphasizing just how unusual it is for the world's strongest heat dome to be centered over the state.
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More background
A heat dome becomes even harder to endure when it stalls in place. In Hall's description, the air pressing downward beneath it gets hotter as it compresses and also loses moisture, which limits cloud growth and removes a common source of relief.
That can mean higher electric bills, more strain on air-conditioning systems, tougher conditions for outdoor workers, and nights that never seem to cool off enough.
One user said, "I don't think we have shut off the air conditioner since April. It is crazy in middle Tennessee".
Another user said, "It's been miserable here."
Even when temperatures fall short of 100, a prolonged run in the 90s can still wear people down, especially if humidity stays high and overnight lows stay warm.
What can be done?
Hall said the system was expected to start shifting, a change that could remove the triple-digit highs from Tennessee even if many places stay in the 90s for a while.
Practical steps include staying hydrated, avoiding strenuous outdoor activity during the hottest part of the day, and checking on older neighbors or anyone without reliable cooling.
Conditions can change quickly when a front finally arrives, and local forecasts can help track both the continued heat and the first real cooldown.
Where can I learn more?
This burst of Tennessee heat is part of a broader pattern of dangerous heat settling over large parts of the U.S. These articles look at other heat domes, record-breaking temperatures, and the risks that come with oppressive days and warm nights.
• Across the eastern U.S., feels-like temperatures of 115 raised the threat from already oppressive heat.
• In the East, a potent heat dome helped shatter temperature records dating back to 1888.
• Ahead of July 4, West Virginia faced highs pushing 100 under a dangerous heat dome.
• Across the U.S., conditions felt just once before returned as a deadly heat wave expanded.
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