A heat wave is building and could reach dangerous levels in parts of the Midwest, the Plains and the Southeast this week.

Fifteen states are under heat advisories, which means temperatures are expected to exceed 41 degrees.

Kansas City and St. Louis in Missouri are under an excessive heat warning, along with Tulsa, Oklahoma; Memphis, Tennessee; and Evansville, Indiana. In these areas, the heat index, or how hot the body feels due to the combined effects of heat and humidity, will reach between 43 and 46 degrees this week.

A 51-year-old man in Granite City, Illinois, died Sunday due to the excessive heat, the Madison County coroner said. Mitsunari Uechi was found unresponsive in his mobile home, where the air conditioning was not working. Police described the residence as “extremely hot,” Coroner Stephen Nonn said in a statement.

Uechi was transported to Gateway Regional Medical Center with a body temperature of 40 degrees. He was later pronounced dead, according to the coroner.

Nonn noted that Uechi “suffered from chronic medical problems that placed him in a higher risk for heat-stress related illness.”

The advisories and warnings will remain in effect until at least Tuesday.

Several high-temperature records have been broken recently.

Wichita, Kansas, hit 44 degrees Sunday. The National Weather Service says temperatures of 44 degrees have only occurred there 10 times since July 1888.

Also on Sunday, the temperature in tornado-ravaged Joplin, Missouri, hit 41 degrees, and in Springfield, Missouri, it topped 39 degrees. Both of these temperatures bested high-temperature records set in the 1980s.

Oklahoma City hit a record high of 42 degrees Thursday, the same day that Tulsa hit a record high of 40 degrees.

High pressure over the Plains is keeping the weather pattern stable, allowing heat to build and suppressing thunderstorms.

Some relief is expected by mid-week as the high pressure system weakens and shifts slightly southeast. This will allow thunderstorms to develop in the central Plains.

Excessive heat is extremely hazardous to human health. According to information on the National Weather Service website, heat disorders can develop when the body heats too quickly to cool itself safely, or when a person loses too much fluid or salt by sweating or dehydration.

Signs of heat exhaustion include heavy sweating, pale and clammy skin, weak pulse, fainting and vomiting.

The agency suggests that people protect themselves from heat disorders by reducing activity during the hottest part of the day, wearing lightweight clothing and drinking plenty of water.

The agency also asks that people abstain from caffeinated or alcoholic drinks. Even meat and other proteins can increase metabolic heat production.

The states under the heat advisory are:

• — Nebraska
• — Kansas
• — Oklahoma
• — Texas
• — Iowa
• — Missouri
• — Arkansas
• — Louisiana
• — Illinois
• — Indiana
• — Ohio
• — Kentucky
• — Tennessee
• — Alabama
• — Mississippi

– CNN.com, temperatures converted into Celsius by WeatherWatch.co.nz