The summer’s below-normal temperatures are being revenged by an early September heat wave which sent temperatures soaring to 95 degrees Thursday while the humidity climbed as high as 50 percent.

The high temperature and humidity produced a heat index of 106, making sunstroke, heat cramps or heat exhaustion possible, said Dave Petrovich, Rockford Weather Service forecaster.

Commonwealth Edison spokesman Paul Callighan said consumers set a 1990 record demand for electricity, using 17,272,000 kilowatts between 4 and 5 p.m. Thursday. The all-time record is 17,459,000 kilowatts, set Aug. 17, 1988.

NIU Weather Service meteorologist Jim Noel said this week’s mercury rose between 10 and 15 degrees above the mid-70s, which is normal for this time of year.

The heat wave is the result of a warm, humid and unstable air system called the Bermuda high which came north from the Gulf of Mexico and the southern states of California and Mississippi, Noel said.

NIU students suffering from unusual heat and humidity should take heart, because the “roller coaster” effect will bring mild temperatures during the weekend, he said.

Noel said the jet stream will soon be dipping south, signalling changes in the weather pattern.

Temperatures will be in the lower to mid-80s today through Monday, with lower humidity, Petrovich said. Temperatures should be in the 70s Tuesday, he said.