St. Charles County to activate sirens during ‘destructive’ thunderstorms


ST. CHARLES COUNTY, Mo. – Starting Sept. 20, St. Charles County Regional Emergency Management (REM) is changing how it will alert residents during severe storms.

REM is teaming up with the National Weather Service (NWS) for the changes. Officials say the change will also cut down on confusion during outdoor warning siren testing.

Here are the changes:

  • The NWS will push Wireless Emergency Alert (WEA) notifications to smartphones if a thunderstorm in an area is categorized as “Destructive.” A storm in this category has at least 2.75-inch diameter (baseball-sized) hail and/or 80+ mph winds. The alert notification will be similar to those issued by the NWS during a Tornado Warning. 
  • When the NWS issues an alert notification for a “Destructive” storm, REM will activate the outdoor warning sirens throughout the county. REM also activates the sirens when the NWS issues a Tornado Warning.
  • REM is moving St. Charles County’s monthly outdoor warning siren test from 9 a.m. to 11 a.m. on the first Monday of the month. This will coincide with St. Louis County’s outdoor warning siren testing time to help reduce confusion for those who live and work along the St. Charles and St. Louis County border.

The NWS says 13of the 22 costliest weather disasters in 2020 were severe thunderstorms. St. Charles County officials say between 2012 and 2021 there have only been seven thunderstorms categorized as ‘destructive’ in the county and say this type of severe weather is rare.

“As a result, issuing this alert and activating the sirens is necessary to protect our community,” says Capt. Chris Hunt, Director of REM.

Officials also explain the “derecho” that his Iowa in Illinois in 2020 packed wind gusts of more than 120 mph. Those winds were stronger than an EF-0 tornado that has wind speeds of 65-85 mph.

Emergency management agencies for St. Louis City and St. Louis County made a similar announcement last week. Sirens will sound in St. Louis City and St. Louis County for destructive thunderstorm warnings.   

For more information on severe weather safety and tips to prepare for any emergency, visit

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