Heat Advisory Issued Across Indiana

STATEWIDE — A heat advisory is in effect across much of Indiana beginning Monday as temperatures rise and heat index values are expected to reach 105 to 108 degrees. The National Weather Service issued the advisory through 8 p.m. Thursday.

Forecasters say the combination of high temperatures and oppressive humidity will make it feel much hotter than the actual air temperature, increasing the risk of heat-related illnesses for anyone spending time outdoors.

“We’re forecasting highs in the lower 90s for now, but one big factor is the humidity,” said Matt Eckhoff, a meteorologist with the National Weather Service in Indianapolis. “We had a lot of rain recently, especially down south, and that moisture is going to add to the humidity already in the air.”

When that humidity combines with the sunshine, Eckhoff said apparent temperatures will approach 105 degrees across central Indiana.

“For that reason, we’ve issued a heat advisory through Thursday,” he said.

Central Indiana’s threshold for a heat advisory is a heat index of 105 degrees. An excessive heat warning is issued when the heat index reaches 110 degrees. Those thresholds vary across the state because different regions fall into different climate zones.

“It’s typically cooler farther north, so their thresholds are a bit lower,” Eckhoff said. “Farther south it’s a bit higher. Here in central Indiana, 105 is our threshold for a heat advisory.”

The upcoming heat wave follows nearly two weeks of repeated rounds of rain and severe storms. Eckhoff said the change in weather is being driven by a shift in the jet stream.

“The jet stream has been basically directly overhead, and that’s a highway for storm systems,” he said. “It has been one after another. That jet stream finally looks like it’s going to lift northward back into Canada. When that happens, the warm air rapidly flows northward, and we’re going to be in a hot and humid air mass basically blasting through the whole week.”

The humidity also makes the heat more dangerous because it limits the body’s ability to cool itself.

“When it’s humid, your sweat doesn’t evaporate,” Eckhoff said. “Your body can’t cool itself or regulate its temperature, so your internal core temperature rises much quicker when you’re also dealing with extreme heat.”

Another concern is the lack of overnight relief. Overnight lows are expected to remain in the low to mid-70s, preventing homes and buildings without air conditioning from cooling down.

“It’ll just get very hot,” Eckhoff said.

He encourages Hoosiers to stay hydrated, limit strenuous outdoor activity during the hottest part of the day, and take advantage of cooling centers if they are available.

“The best thing to do is just be aware of the heat that’s coming, find ways to cool down, and drink plenty of water,” Eckhoff said. “Some counties are starting to open cooling centers. If you don’t have air conditioning, take advantage of them.”