HORIZON CITY, Texas — The cinderblocks that make up Maria Teresa Escamilla's new home will do little to shield her from the triple-digit heat that has been scorching West Texas. She has no electricity yet, and the roof is not properly attached, leaving the interior exposed to the elements.

Escamilla has been living in an air-conditioned apartment that she can no longer afford. But when the lease ends in two weeks, she has to move — a day she dreads because it means she'll have no escape from the searing temperatures.

"This is what I have to look forward to," she said. There will be no air conditioning and an unbearable number of mosquitoes at night.

With much of the nation in the grip of a broiling heat wave, few people are hit as hard as the poor, and few places are poorer than the ramshackle communities along the Texas-Mexico border known as "colonias."

The misery was widespread Monday, with the worst conditions blanketing a broad band from Texas to Minnesota and Dakotas. Seventeen states issued heat watches, warnings or advisories. And the heat index easily surpassed 100 degrees in many places: 126 in Newton, Iowa; 120 in Mitchell, S.D.; and 119 in Madison, Minn.

The high temperatures were nearly certain to persist for the entire week. Forecasters expected the extreme discomfort to spread soon to the East Coast.

In towns large and small, the withering heat was cruelest to those who could not afford air conditioning.

Built at the edge of the desert, the colonias often lack electricity and running water. People bought the land before zoning regulations were adopted, hoping that utility services would follow.

To finance her house, Escamilla, who is 62, had to take out a loan against her funeral services and buy building materials recycled from demolition sites in Ciudad Juarez, across the border from El Paso.

Norma Salazar, who shares a tiny trailer home with her husband and six children in Horizon City, on the outskirts of El Paso, has to rely on an evaporative cooler, a cheap alternative to air conditioning that sucks the hot, dry desert air through a mesh of water-soaked fibers.

But it only cools half of the trailer, and when the heat climbs above 100, not even that.

"When it gets really hot, we turn on the fans and stay inside," Salazar said.

Going to a library or a mall to keep cool is not an option because the car doesn't have air conditioning. "So getting there is even worse than just staying inside, not moving," she added.

In downtown Minneapolis, where the heat index reached 106 degrees, the Salvation Army's Harbor Light Center threw open its doors for anyone who needed to cool off and drink a glass of ice water.

Executive Director Bill Miller said he allowed about 200 people who slept at the shelter Sunday night to stay instead being asked to leave in the morning.

"We don't have them leave when it's this hot," he said. "It's hot enough to get dehydrated, especially if you're drinking. In this heat, it could kill you."

Betty Jean Horlacher-Bainbridge-Roswell slept at the center Sunday night before venturing out into the heat Monday morning. She was six blocks away when she was nearly overcome.

"I almost passed out because of the heat," the 55-year-old woman said, explaining that she suffers from diabetes, epilepsy, high blood pressure and other health issues. She pushed the baby-stroller filled with her belongings back to the center.

Had it been closed, "I would have probably died," she said.

Chicago officials opened six cooling centers, many of them in lower-income neighborhoods, along with hundreds of air-conditioned public buildings such as libraries, park facilities and police stations.

Anne Sheahan, spokeswoman for the city's Department of Family and Support Services, expected the number of people seeking refuge at the centers to climb in step with the temperatures, which were not expected to drop below the mid- to upper-90s throughout the week. The city was also offering rides to cooling centers.

Chicago authorities stepped up their high-heat precautions after a 1995 heat wave killed more than 700 people in less than a week. Now temperatures above 90 degrees trigger an emergency plan that includes city workers calling and visiting the frail and elderly.

Chicago school officials said they were making 1,500 fans available to schools that were not fully air-conditioned and asked teachers to keep blinds closed, move classes to cooler rooms and ensure students have water at all times.

Spokeswoman Marielle Sainvilus said the district would not cancel summer school classes during the heat because many students are poor.

"Unfortunately a lot of our kids do not have air conditioning at home," she said. "And they'll also get nutrition and a safe environment."

In East St. Louis, Ill., a mostly black city that's among the nation's poorest, 79-year-old Bernice Sykes spent Monday in a soup kitchen that had been pressed into service as a makeshift cooling center.

Sykes, a retired restaurant worker living on Social Security income, figured she had little choice to seek relief: One of her two tiny fans failed Sunday in her $500-a-month-efficiency apartment, which has no air conditioning.

"I want to get out of there as quick as I can," she said Monday. "Right here, I feel good. But I've got to use that one fan when I get home. It's just so hot."

The Society of St. Vincent de Paul, which runs the soup kitchen, was hustling to offer other ways to beat the heat, including deploying one of its two air-conditioned buses as mobile cooling stations and handing out water and wet rags for use as neck compresses.

"It's pretty brutal. When I got up this morning, it already was 80 degrees," said Pat Hogrebe, who works at the kitchen. "I'm hoping, praying for the cool weather angel to come. Today, it's just not here."

Even powerful fans can be of limited usefulness.

"When its 95 degrees out, and the fans blow out hot air that's not enough to drive down body heat," said Bobby Mukkamala, an ear, nose and throat doctor from Flint Township, Mich., a once-thriving auto manufacturing town where the economy has steadily declined.

In Oklahoma, the intense heat has generated a flood of applications from elderly and low-income residents for money to help pay their utility bills.

The Summer Cooling Assistance Program was launched July 11 and ended just three days later when all $22 million in the budget were paid out, said Rick Steen, director of field operations for the Department of Human Services in southwestern Oklahoma.

Back in El Paso, Grace Ortiz heads a task force that tries to prevent heat-related deaths. She says the group has given out more than 400 fans this year and expects to distribute twice that number before the summer is over, mainly to the elderly and needy families with children.

"They are the most at risk," Ortiz said. "Sometimes a fan can be the difference between life and death."

Associated Press writers Tammy Webber in Chicago, Jim Suhr in St. Louis, Chris Williams in Minneapolis, Tim Talley in Oklahoma City and Corey Williams in Detroit contributed to this report.