Under the revised Johnson County outdoor warning system guidelines, sirens are sounded for:
- Tornado Warnings, either Doppler radar indicated or reported by a trained spotter.
- Severe thunderstorms Warnings if they contain winds of 70 mph or greater (potential for whole trees to snap or uproot), or contain, 1 inch (Golf ball sized) hail or larger (potential for windows to break).
- The same tone will be used for all weather-related threats throughout the County.
- Sirens may be sounded multiple times to convey a continued or new threat(s).
- We do not sound an all-clear signal with the sirens. (People should be indoors monitoring the weather.)
- Sirens are tested on the first Wednesday of each month starting at 10 am.
- Sirens run for 3 minutes once activated
- The County is zoned into four (4) zones for activation(s). Those are Red for the North part of the County, White for the Central part of the County and Blue for the Southern part of the County. A Green zone is used for Warnings that threaten the entire County or cross all three (3) zones. City specific sirens may also be activated. Presently rural Johnson County has four (4) outdoor sirens and plans to add another six (6) using grant funds, later in 2012. This will cover the more densely populated or heavily used recreation areas of the County.
Advanced Spotters’ Field Guide
Basic Spotters’ Field Guide
Johnson County Siren Guidelines, February 2012
Johnson County Tornado Siren Coverage Map