The day started relatively normal according to late August standards. However, temperatures and dewpoints were above normal. Temperatures soared into the low 90's as dewpoints approached 80. At around 1 P.M., the National Weather Service did issue a Severe Thunderstorm Watch for northern Illinois until 8 P.M. However, no one expected what was to come.
In DeKalb County, a supercell thunderstorm formed a tornado near Oswego, Illinois. It was an ordinary tornado of about F2 strength. As the tornado moved into Will County, it strengthened into an F4. It then began to move into Plainfield, Illinois at around 3:45 P.M. Thankfully, the schools had already released the students but extra-curricular activities were starting. Plainfield High School had football practice, but the coach heard of the threatening weather approaching and decided to move it inside. Only one of the 29 deaths occurred at the school. A teacher saw the tornado approaching and decided to stand there and watch it. He was killed.
The tornado then aimed at Crest Hill, Illinois. It caused F3 or F4 damage. Even though this tornado was devestating, it could have been even more catastrophic.
The National Weather Service was caught off guard, mainly because of its grueling work load. There were only two NWS offices in Illinois in 1990: Chicago and Rockford. Thirteen and a half years have passed since the Plainfield tornado. Hopefully, when another F5 tornado occurs, we will not be caught off guard.