KANSAS CITY, Mo. (AP) -- Heat indexes were back in the triple digits Monday in northeast Kansas and Missouri, where heat was blamed for four deaths last week.

The National Weather Service issued heat warnings Monday for much of the area with temperatures expected to be in the upper 90s to about 100 through Friday. Nighttime lows, which would likely hover around 80 degrees, were unlikely to provide much relief.

Heat indexes, which measure how hot it feels, were expected to fall in the 105- to 115-degree range because of high humidity in the region, said Noelle Runyan, meteorologist for the National Weather Service.

The latest heat wave follows one early last week in which four deaths in Kansas City were blamed on temperatures that were well into the 90s. The heat abated some late last week, only to rise into the 90s again Sunday.

"It is August. It's summertime in the Midwest, and we do expect heat. But this is extreme," Runyan said. "This is going to be persistent, extreme heat."

Extreme heat warnings also have been issued for southeast Nebraska and southwest Iowa, and heat advisories were issued for spots all the way down to the Gulf Coast, she said.

Thunderstorms forecast for Tuesday night in some areas could reduce temperatures slightly.

One or two days of excessive heat is more common and easier to manage than a heat wave that lasts several days, Runyan said.

Across the region, officials have been taking precautions to deal with the high temperatures. St. Louis Mayor Francis Slay's office planned automated telephone calls with tips for residents on dealing with hot weather and reminding them to check on friends, neighbors and relatives who might struggle in the heat.

The Kansas City Chiefs pushed afternoon practice for training camp in St. Joseph back to 6 p.m. "for the safety of Chiefs players and fans."

And Johnson County, Kan., opened all its libraries as cooling centers. In the St. Louis area, 75 cooling centers were opened with air-conditioning and cold water.

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Associated Press Writer Jim Salter in St. Louis contributed to this report.