Hurricane Harvey Over Chicago

Sometimes it is hard to appreciate the scale of the disaster from the rainfall of Hurricane Harvey. To put this into perspective for us in Illinois, here are the 5-day rainfall totals of Hurricane Harvey transposed from Houston to Chicago. Amounts of 40 or more inches would have covered most of the Chicago area and stretched westward towards Rockford and beyond. Amounts of 20 inches or more would have covered most of Illinois north of Interstate 80 and extend into southern Wisconsin.
Imagine …

  • the number of people that would have to be evacuated and how far they would have to go get away from the floodwaters,
  • the pollutants and raw sewage in all that floodwater,
  • the amount of damage to Chicago and the region – damage to businesses, homes, schools, hospitals, airports, highways, railroads, etc.,
  • the amount of time and money it would take for Chicago to ever recover from such a disaster,
  • the ecological damage to Lake Michigan and the Illinois River Basin as these flood waters pushed chemicals and debris far and wide,
  • getting a year’s worth of rain (and more) in 5 days – the statewide average precipitation in Illinois is 40 inches.

By comparison, here are the rainfall amounts from the July 17-18, 1996 storm that hit northern Illinois and set the record for the most rain in 24-hours, 16.94 inches at Aurora. Six people in Illinois died from this event and the damages were in the $600-$700 million in 1996 dollars. While this storm caused substantial damage in the Chicago area, the rainfall totals were much smaller than Hurricane Harvey and covered a smaller area.

Sorry for the way the map looks, it was hand drawn and used a variety of hard-to-find rainfall measurements. Today we have access to much more data,  including CoCoRaHS and radar-based precipitation estimates.

While Illinois can receive rain from tropical systems, they are usually weakened by the time they arrive and far away from abundant sources of moisture like the Gulf of Mexico. Here are the 5-day totals from one of the largest storms to hit Illinois in recent years – the remains of Hurricane Ike in 2008. Although the heavy rain was widespread, the amounts were still much smaller than from Harvey.
Here are some other noteworthy large-scale storms in Illinois. Click to enlarge.

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