Floods can take several hours to days to develop. Twenty people in Illinois have died from floods since 1985. Twelve of the 20 deaths occurred in vehicles. Dam failures or ice jams can cause severe flooding. The most dangerous type of flooding is a flash flood.
Flash floods can sweep away everyone and everything in their path.
Flash floods can take only a few minutes to a few hours to develop. Most flash floods are caused by slow-moving thunderstorms. Flash floods occur most frequently in mid to late summer. Extreme cold often accompanies a winter storm or is left in its wake. Prolonged exposure to the cold can cause frostbite or hypothermia and become life-threatening.