Indiana Under Extreme Heat Warning

STATEWIDE — An extreme heat warning is now in effect across Indiana, replacing the previous heat advisory as forecasters warn the combination of high temperatures and humidity will create dangerous conditions through the end of the week.

Mike Ryan with the National Weather Service office in Indianapolis says the decision to upgrade the alert is tied to how long the heat is expected to last and the impact of heat index values.

“The reason we’ve done that is because of the extended nature of this excessive heat,” Ryan said. “Heat indices are expected to top out between 105 and 110 degrees.”

Ryan says many locations, including Indianapolis, reached heat index values around 105 degrees Monday, with afternoon heat indices expected to remain in the triple digits over the next several days.

“When we get to points where we’re talking about heat indices, that’s that feel-like temperature of your body getting up into that 105, maybe 110-degree range,” Ryan said. “That’s substantial even if you’re a healthy individual.”

Ryan says people who work outside or spend long periods of time outdoors face increased risks if they are not staying hydrated.

“If your job takes you outside in this heat for an extended period and you’re not drinking the amount of water that you need to, this is a level of heat that can overwhelm even somebody healthy,” he said.

The heat can also be dangerous for people who may not have access to air conditioning.

“If you live in a building or an apartment that maybe doesn’t have air conditioning, that’s a group of people that would be considered vulnerable to this kind of heat,” Ryan said.

One factor making the heat more challenging is the lack of overnight relief. Ryan says temperatures are not dropping much after sunset because of the weather pattern keeping hot air trapped over the region.

“We’ve had a ridge of high pressure in the upper level of the atmosphere that has expanded and is in the process of further expansion across the Mississippi and Ohio valleys,” Ryan said.

That ridge is what meteorologists refer to as a heat dome. Ryan says sinking air beneath the ridge is helping maintain the hot and humid conditions.

The dry weather has provided one benefit by allowing water levels to recover in some areas, but Ryan says there is also a downside.

“The unfortunate thing that also did was that bumped up the humidity levels because there’s so much moisture in the lower levels of the atmosphere,” Ryan said.

Ryan says the current weather pattern is also limiting storm activity, with thunderstorms staying north of Indiana.

“Those thunderstorm complexes are currently going up through the northern Plains, the upper Midwest, up in Canada, coming back down across New England,” Ryan said. “It’s because the ridge is in place over the Great Lakes, Ohio Valley and Mississippi Valley, and those storms are unable to move into this area.”

Forecasters are watching for a better chance of rain and storms later this week, especially Friday into the weekend. Ryan says the timing and location of those storms remain uncertain.

Indiana Under Extreme Heat Warning was originally published on wibc.com