ST. LOUIS (AP) -- At least two people have died due to recent blistering temperatures across the Midwest, and health officials urged residents Tuesday to keep an eye on those who could be vulnerable as the mercury continues to rise.

The National Weather Service issued excessive heat warnings for portions of Missouri, Arkansas, Kansas and Oklahoma through Wednesday night.

Forecasters said temperatures would top 100 degrees across the region Tuesday, and in some areas approach 110. Compounding that, the high humidity common to the region in the summer could make it feel 10-15 degrees hotter than the thermostat reading.

"Today and tomorrow are going to be pretty nasty," National Weather Service meteorologist Ben Miller said.

The Kansas City, Mo., Health Department said heat was likely to blame in the deaths of two people, but did not release their names or other details, saying the deaths were under investigation.

Emergency Medical Services Authority in Tulsa, Okla. reported seven heat-related calls on Sunday, none of them life-threatening.

"With the heat expected to continue this week, residents need to check on neighbors, friends and relatives as heat-related illnesses and deaths can be prevented," said Dr. Rex Archer, Kansas City's health department director.

People who don't have air conditioning were urged to try to get somewhere that does, or at least keep their homes well ventilated with fans. Those who work outside were urged to be extra careful.

St. Louis -- where the temperature hasn't surpassed 100 degrees since Aug. 15, 2007 -- was expected to reach 102 degrees Tuesday, while the forecast for Oklahoma City, Okla. was 105.

"It's August," Miller said. "We've got a ways to go yet."

On Monday, the 108-degree reading in Wichita, Kan. broke the city's old record of 106 degrees, set in 1970.

Arkansas was sweltering, too. Monday highs reached 107 degrees in Blytheville and 106 in Little Rock. Freedom, Okla. felt temperatures rise to 109 degrees, while it was 108 and 107 elsewhere in the state. Missouri was hottest in the southwest corner of the state -- Mt. Vernon reached 104 degrees Monday.

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Associated Press writer Ken Miller in Oklahoma City, Okla. contributed to this report.