BOONE COUNTY â Effective Aug. 2, Boone County's Office of Emergency Management (OEM) will update its policy relating to when outdoor warnings will be activated. From that point on, outdoor warning sirens will be activated in Boone County when the weather service issues a severe thunderstorm warning with a âdestructiveâ tag included in the warning language. Boone County's outdoor warning sirens The National Weather Service will put the destructive tag on the warning if there is a threat of baseball-sized hail and/or if there is a threat of winds up to 80 mph or higher in Boone County. The system will now include a tier program for the level of the storm.