DeKALB | The continental United States sweat through its second hottest July ever recorded this past summer with droughts drying up the plains and the southeastern U.S.

However, an expert says this summer’s warm-up has nothing to do with global warming.

“There is no known relationship between our year-to-year changes in temperature and precipitation and ‘global warming,'” said assistant geography professor Mace Bentley. “In addition, climatologists simply do not know how our climate system will evolve as greenhouse gases increase. It is quite likely that some areas of the world will indeed warm and could warm substantially. However, other regions may actually cool down.”

Some parts of the country have, in fact, experienced a “cool down,” but most U.S. temperatures were above average in June and especially in July. Temperatures were below average in August in those same areas.

Illinois and neighboring eastern states experienced a normal, and in some cases, cooler June. But August temperatures for northern Illinois were above normal. This was the result of the jet stream, a current of fast moving air in the upper level of the atmosphere.

“Changes in the persistent weather patterns in the summer are almost always dictated by where the jet stream sets up,” Bentley said. “This year, the central and western U.S. were generally south of the jet stream where temperatures are typically above normal and precipitation below normal.”

Areas north of the jet stream, such as DeKalb, are usually cooler.

“Also, much of the eastern U.S. had quite a bit of rain this summer, and the resulting clouds and rain helped keep temperatures down,” said NIU staff meteorologist Gilbert Sebenste. “Decent rains in our state, and to an extent in DeKalb, in the first half of the summer made a few days cooler than average.”

“In August, the jet stream retreated north of Illinois, placing us in the warmer air and also away from most of the weather systems that could’ve given us rain and cooled us off,” Bentley said.

As far as monthly and yearly averages go, DeKalb has a lot of variability. So this summer’s weather is nothing out of the ordinary.

“What we are seeing is probably just a normal variance in our climate, albeit on the high side of recorded changes,” Sebenste said. “Unfortunately, like a recession, it’s very difficult to tell you are in a permanent climate change until you are actually experiencing it.”

“[These] climate changes are not unusual,” Bentley said. “In fact, I would not call them climate changes at all… these large differences were simply due to the setup of larger-scale weather patterns (i.e. jet stream). We have a lot of year-to-year variability.”

Stephanie Wise is a City Reporter for the Northern Star.