Paul Gross explains: Why do sirens sound if there's no tornado warning?

So you've heard tornado sirens - but there isn't a tornado warning: what's the deal?

We are all familiar with the tornado sirens:  When you hear one, you head to the basement or your place of safety as quickly as possible, because a tornado is either on the ground, or a severe thunderstorm capable of producing a tornado has developed.

However, siren philosophy has changed recently, and many communities and counties now also sound their sirens when a severe thunderstorm with anticipated 70 mph or greater wind threatens.


Because a 70 mph wind gust from a thunderstorm is comparable to the wind in a weak tornado.

If the sirens are sounded for a weak tornado, why wouldn't you sound them for a severe thunderstorm with wind as strong as in a weak tornado?  

70 mph plus wind can snap off large trees and power lines, and cause some structural damage ... they are very dangerous storms, so you should still seek shelter whenever you hear the sirens.

Back on July 2nd, 1997, a very severe thunderstorm roared through the Grosse Pointes with 100 mph straight-line wind gusts, blowing a gazebo with thirteen people in it into Lake St. Clair, killing five of them.  High-end severe storms even without tornadoes are still high-impact storms, so keep this in mind the next time you hear the sirens.

About the Author:

Local 4 meteorologist Paul Gross was born in Detroit and has spent his entire life and career right here in southeast Michigan. Paul has researched, written and produced eight half-hour documentaries for WDIV, as well as many science, historical and environmental stories.