Excessive Heat in Jefferson, Illinois

A strong and very persistent high in the upper levels of the atmosphere was responsible for seven consecutive days of heat indices at or above 105 degrees. The high was centered over the Lower Ohio Valley for the first few days of the heat wave, then it shifted slightly southward and weakened. The summer as a whole was among the hottest on record. The heat index peaked mainly between 105 and 111 degrees at the Marion and Carbondale airport sites during each afternoon of the event. Similar values were observed elsewhere. Heat indices during the early morning hours were mostly in the mid to upper 80's. Hospitals reported that cases of heat exhaustion were quite low. Seven heat-related illnesses were treated at a Mount Vernon hospital. Only a few cases were reported in the Harrisburg area. Heat illness information was not available from other hospitals.