Extreme Heat Pushing Radio Signals Far Beyond Normal Range; IN Tornado Sirens Activated By IA Alert

It was 3am in north-east Indiana’s Huntington county when the outdoor emergency alarm went off on 1 July. The only issue? There wasn’t a storm, tornado or any other emergency weather event forecast or present anywhere for hundreds of miles.

“It happened right in the middle of the night. I woke up at around 5am and saw on our Facebook page multiple comments [of people writing], ‘Hey, our siren went off last night.’ I thought, ‘That’s weird,’” recalled Thomas Fuller, Huntington county’s deputy director for emergency management. “When there’s an activation, it’s usually by the Huntington county dispatch center. But this siren activated all by itself due to the radio signals all the way from Iowa.”

Amid the heat dome weather event that affected hundreds of millions of people in the midwest and on the east coast this month, strange and little-observed communications interruptions have started to unfold. The emergency alarm in Huntington county received radio signals from 300 miles west that accidentally matched the activation code for the siren, said Fuller. In Ohio, residents driving in their cars, their radios tuned to the local news and music, were warned that they could find themselves abruptly listening to radio stations hundreds of miles away, or their coverage simply blanked out.

These events are down to the high temperature’s effects on tropospheric ducting, the atmospheric weather phenomenon that can facilitate radio, television and microwave signals traveling for hundreds of miles. The ducting, also known as tropospheric propagation, typically lasts anywhere between minutes to several hours, but sometimes longer, depending on the weather and atmospheric conditions in a particular location.

EDIT

https://www.theguardian.com/us-news/2026/jul/13/heat-dome-radio-signals-us-midwest