Weather news
18 September records set as weather balloons measure the South's heat dome
By Ryan Hall, Y'all Weather Desk ยท Published
Written by our automated news desk from National Weather Service data.
Key points
- Where: 18 balloon sites between Oklahoma City and New York, out of 41 that reported from the Rockies to the East Coast.
- When: the evening balloon launches that followed our Sept. 16 heat dome post.
- What: the highest September 500 millibar height in each site's record. Birmingham and Atlanta led at 6,010 meters (19,718 feet).
- What it means: the dome was not just a hot forecast. Instruments flew through it and measured it, and it was taller than anything on record for September at those sites.
Weather balloons measured the highest September readings on record for the halfway point of the atmosphere at 18 of the 41 sites that reported from the Rockies to the East Coast. The records ran from Oklahoma City to New York, and Birmingham and Atlanta led at 6,010 meters (19,718 feet). That was higher than the 19,665 feet on our Sept. 16 heat dome poster.
That height is the 500 millibar level, the spot where half the atmosphere's weight sits below you. A heat dome pushes it up, and these balloons measured by how much.
What the balloons actually measured
The evening weather balloons measured how high you had to climb to reach the 500 millibar level, the halfway point of the atmosphere. At 18 locations, that level was higher than ever recorded there in September.
In Birmingham, you had to go almost 4 miles straight up to get above half the atmosphere. Atlanta matched that at 6,010 meters. Both sit above the 19,665 feet we showed on the Sept. 16 poster.
How the records stack up
The picture above draws the dome as a raised surface over the South. The balloon sites stand on it, and each one shows the height its balloon measured.
Eighteen of the 41 balloons that reported set a September record for their site. That is a big share for a measurement that has been taken for decades. Some records stretch back to 1947 and 1948, so the dome beat marks that had stood for generations.
The 6,010 meter reading is a measurement, not a forecast. The balloons flew, the instruments reported, and the numbers are in.
Where things stand now
That was September. Today, Tuesday, Nov. 10, the severe weather picture is quiet. There is a Level 1 of 5 (Marginal) risk along the Texas coast, with isolated hail possible tonight. Wednesday, Nov. 11, has a Level 1 risk across parts of Indiana, Kentucky, Tennessee and Illinois, including Indianapolis and Nashville. You can follow the latest on our severe storm outlooks and check active warnings. If you want a heads-up when the weather turns, sign up for free Y'all Alerts.
Bottom line
Weather balloons confirmed that the September heat dome lifted the atmosphere higher than ever recorded in September at 18 sites. Birmingham and Atlanta led at 19,718 feet, with records falling from Oklahoma City to New York.
More on Weather records, September 2026
Places in this story: Oklahoma City, OK