A SEVERE THUNDERSTORM WATCH means severe thunderstorms are possible during the time the watch is in effect. Watch the sky, stay alert for warnings, and be prepared to seek safe shelter.
A SEVERE THUNDERSTORM WARNING means a thunderstorm capable of causing property damage and injury has been sighted or detected by radar. Go indoors immediately and stay away from windows and doors.
A SIGNIFICANT WEATHER ADVISORY means a strong thunderstorm with hail less than 1.00" in diameter and/or wind gusts of 45 to 55 mph is anticipated. Go indoors and stay alert for an upgrade to a warning.
There are two kinds of damaging wind that a severe thunderstorm can produce:
a “Straight-line” wind and a “Downburst” wind. These two types of damaging wind can cause the same kind of destruction as many of the tornadoes which occur in Illinois, so Severe Thunderstorm Warnings need to be taken SERIOUSLY!
In the past 10 years, 17 people have died in Illinois due to high winds.
Since 2009, there have been 71 people injured in Illinois from severe thunderstorm related wind.
Photo by Paul Hadfield
Very large hail, the size of golf balls or larger, is not only very destructive, but it occurs with the strongest thunderstorms called “Supercells”. These thunderstorms can also produce extensive wind damage and strong or violent tornadoes. Every year in the state of Illinois, supercell thunderstorms produce destructive hail ranging in size from baseballs to grapefruits.
Photo by Larry Frank