It reached 90 degrees on June 5, 1988 at the National Weather Service (NWS) near Negaunee. It was the first 90 during the long, hot summer of 1988. Warm, dry weather began in May. The mean temperature was 4.5 degrees above average, while rainfall was only a third of the long-term average. The month ended with four consecutive days above 80 degrees. June 1988 registered four more 90-degree days after the one on the 5th including a 93-degree high the next day. The heat in June came with little humidity. In fact, the month brought less than three-quarters of an inch of rain??only 22 percent of normal. The dryness helped build and exacerbate the heat during the summer of 1988. The long-term drought index showed the northern Plains, Mississippi and Ohio Valleys in the grip of severe to extreme drought (Image above).
The heat continued to build and expand from the Plains into the eastern U.S as the summer wore on. By the time it was through, there were 13 days with temperatures of 90 degrees or above at the NWS. The long-term average is only three days. In Chicago the temperature went to 90 or above on a record 48 days; the average is 23.
The summer of 1988 was a memorable one, yet an examination of the monthly departures shows nothing spectacular. June 1988 ended 2.7 degrees above average; July was four degrees above normal, while August was 2.4 degrees above average. There were several cool shots during the summer that made it as far south as Upper Michigan. These cool spells lasted several days at a time and brought the monthly average down.
This year??s moisture situation is much different than back in 1988 (Image 2). In fact, it??s much different than even last year (Image 3). Last year there was extensive drought to our south in the Corn Belt. That area was a breeding ground for heat. This year, the area is soaked. That means while there will eventually be some warm, maybe even hot days, the heat will most likely not be as extreme or long-lasting as last year.