Tornado sirens blared across Elmhurst, Villa Park and dozens of other DuPage County communities at 3 a.m. Tuesday, Aug. 18, jolting residents awake. There was no tornado. No severe weather of any kind.

A DuComm staff member accidentally activated the countywide siren system while conducting a planned test of the technology, DuPage Public Safety Communications confirmed in a Facebook post at 9:24 a.m. Tuesday, as NBC Chicago reported. The tests are designed to check the system's functionality without actually sounding the sirens.

"As soon as the error was realized, DUCOMM staff deactivated the sirens. We regret that our error caused unnecessary interruption or confusion," the agency said.

The false alarm came exactly one week after a derecho with 70 mph winds tore through DuPage County on Aug. 11, triggering real tornado warnings for Elmhurst, Villa Park and Oakbrook Terrace. That timing made Tuesday's 3 a.m. sirens especially unnerving for residents who had just lived through actual severe weather.

What happened

Villa Park police were among the first to respond publicly, posting on Facebook shortly after 3 a.m. that sirens had been accidentally activated in many of the county's towns and that there was no weather emergency. Residents in Downers Grove, Wheaton, Darien and Glen Ellyn also reported hearing the sirens, according to NBC Chicago.

The National Weather Service Chicago office posted on X that nothing had been triggered from its office, adding that it was "hearing this may have been countywide per several other people."

The Village of Downers Grove confirmed on X that DuComm had set off the siren inadvertently while testing the system.

Why sirens sounded at 3 a.m.

DuPage County's standard monthly siren test takes place on the first Tuesday of each month at 10 a.m., according to Fox 32 Chicago. The Aug. 18 activation happened outside that window because DuComm was running a behind-the-scenes technology check, not a public test. The staff member's error turned what should have been a silent diagnostic into a live countywide alarm.

In May 2025, DuPage County launched a new automated siren system designed to activate based on National Weather Service warnings without human intervention. DuComm Deputy Director Tyler Benjamin said in May 2025, when the system launched, that the old process required someone to manually read an NWS alert, interpret the warning area and activate sirens from a map.

The upgrade was meant to speed response times and improve precision. DuComm has not said whether the incident will prompt changes to its testing protocols.

What residents should know

The false alarm required no action. DuComm has not announced any review of its testing procedures, and no follow-up public meeting has been scheduled. Residents who want updates can monitor DuPage Public Safety Communications' Facebook page.