It will feel like a sauna outside as the heat index exceeds 105 degrees Tuesday in more than a dozen states.

The combination of high heat and oppressive humidity began reaching dangerous levels over the weekend, spreading from the Midwest to the Gulf Coast.

While temperature may not be record-breaking, highs will hit well into the 90s to around 100 degrees in southeastern South Dakota; the southern half of Iowa; most of Illinois and Indiana; far southern Michigan; northwestern Ohio; western Kentucky; far western Tennessee; much of Mississippi, Arkansas and Louisiana; as well as eastern portions of Texas, Oklahoma, Kansas and Nebraska. The National Weather Service has issued heat advisories for all of these places.

Add the abundant humidity and the heat index will range from 100 to 109 in the advisory areas. Of particular concern are western Mississippi, northeastern Louisiana and southeastern Arkansas where an excessive heat warning is in place. While the advisory shouldn’t be taken lightly, the warning should be taken even more seriously. The heat index in the warning areas could reach 110 to 115 degrees.

In these conditions, the ability for a driver’s body to cool itself is challenged. When the body heats too rapidly to cool itself properly, or when too much fluid or salt is lost through dehydration or sweating, body temperature rises and a driver may experience a heat-related illness.

All drivers should be sure their rigs are in good condition so their air conditioning, or their trucks themselves, don’t break down. Heat safety tips are available here.

Lanes of concern

Interstate 80 from Grand Island, Nebraska, to Toledo, Ohio
Interstate 29 from Vermillion, South Dakota, to Kansas City, Missouri
Interstate 70 from Topeka, Kansas, to Indianapolis
Interstate 40 from Fort Smith, Arkansas, to Memphis, Tennessee
Interstate 20 from Monroe, Louisiana, to Jackson, Mississippi
Interstate 10 from Lafayette, Louisiana, to Pensacola, Florida
Interstate 55 from Memphis to Pontiac, Illinois

Click here for more FreightWaves articles by Nick Austin.

You might also like:

Long view: Preparing logistically for extreme weather

Top 5 US spots for truck-animal collisions

Hot Shots: Fierce fires, ferocious floods, train derailments and more