Four-year-old Giancarlo Sanchez plays in a water fountain in the Columbia Heights neighboorhood of Washington to beat the heat gripping the nation July 20, 2011.[Photo/Agencies]

CHICAGO - A searing heat wave in the central and southern United States has killed at least 22 people this week, and forecasters  on Wednesday said the heat was moving east and could last for weeks.

The National Weather Service said 141 million people in more than two dozen states were under a heat advisory or warning because of the soaring temperatures. The country's midsection has been scorched off and on since late May.

In Wichita, Kansas, forecasters warned temperatures would hit at least 100 degrees Fahrenheit (38 degrees Celsius) every day through Tuesday.

"It's just draining, physically draining," said Chris Vaccaro, a Weather Service spokesman.

The inferno moved into the mid-Atlantic states. Temperatures reached above 90 degrees F (32 degrees C) in Washington, D.C. and were expected to hit 100 degrees on Thursday.

Meteorologists said the heat wave could last into August over much of the eastern United States.

The cumulative effects  in terms of lost lives, stress on the power grid and damage to roads and bridges could eclipse the effects of the deadly heat wave of 1995, which claimed hundreds of lives in Chicago alone, AccuWeather.com predicted.

"When all is said and done, with the number of days of extreme heat and humidity of the current heat wave, it may be more significant and impact a larger area," said AccuWeather's Jim Andrews.

Hospitals in Wichita treated 25 heat-related illnesses, according to the National Weather Service. In Des Moines, Iowa, 16 people have been hospitalized because of this week's high temperatures.

The high heat and humidity have been stressing U.S. crops, particularly corn, which is now in a key growth stage, and endangering livestock. Up to 1,500 cattle have died in South Dakota because of the heat wave, according to the state's veterinarian, Dustin Oedekoven, and he expects that number to rise.

In Indianapolis, homeowners were being asked to stop watering their lawns through at least Sunday.