Ken Scheeringa has seen a lot of things working in the state climatology office at Purdue University over the years. Even he admits it has been a while since he has observed this kind of extended period of heat in Indiana.
"Our best comparison would be 1998, when we had days over 100 degrees F," he recalls. The difference this time is that besides being hot, it's also humid. "In 1988 we didn't get the humidity with it like we are this time," he notes. "It's the humidity that makes everyone and everything so miserable."
To make matters worse, he doesn't look for a break anytime soon. "We will see some slight cool-offs and false –hope teasers, but it appears the extreme heat will stay with us, at least for the next couple of weeks," he says. "As long as the dome of high pressure sits over Indiana, most storm tracks will go around us."
So why so much heat? "It's likely coming out of the situation that started in Texas," he explains. "The areas was so hot for so long, the heat finally busted out into the Great Lakes and other states, including Indiana."
Asked if it is related to La Nina, Scheeringa says only in a minor way. However, that needs explanation. "The La Nina has ended," he says. "It ended about a month ago and all data shows that. However, there is a lag phase before it transitions to another phase. We're in that phase right now. It appears that we just happened to get caught in the lag phase, plus the Texas heat at the same time:
La Nina is a Pacific Ocean situation where waters are cooler than normal. It will be followed by El Nino, where waters are warmer than normal. The temperature of the water affects atmospheric pressure, which in turn affects circulation patterns around the world. The problem is that these cycles are erratic. It could be one or more moths before El Nino begins and establishes a different type of weather patterns.
Jim Newman, the former Purdue agronomist who helped study and first explain the cycle, always noted and stressed the lag time. It can easily last up to three months according to his former research. In the meantime, it's important to point out that La Nina itself, when active, is often associated with drought.