CHICAGO – Oppressive heat that blistered California last week remained parked over the Midwest on Monday, prompting communities to throw air-conditioned buildings open to the public and endangering millions of people with outdoor jobs.

Temperatures across the Midwest and Plains flirted with or exceeded 100 degrees, and the heat index – a measure of temperature plus humidity – passed 110 degrees in spots. The National Weather Service issued heat warnings for such cities as Chicago; Cincinnati; Dayton, Ohio; and Tulsa, Okla.

The Midwest could get some relief by Wednesday, but the worst of the heat was expected to drift into the Northeast on Tuesday, bringing scorching temperatures to New York, Washington and Boston.

Chicago resident Tony Tesfay, 43, rode his bicycle first thing Monday to one of the city’s cooling centers – air-conditioned buildings opened to the public to prevent a repeat of 1995, when a heat wave killed 700 people.

“I was pedaling slow, not too hard, so I could keep hydrated,” he said.

In Cleveland, temperatures climbed so high by evening rush hour that the city closed a bridge at the Cuyahoga River because the heat was causing the steel to expand and the bridge’s parts could not fit properly together.

Cities across the Midwest urged neighbors to check on the elderly and disabled. Utilities expected to set records for power usage and asked customers to conserve electricity.

In Chicago, officials made available a special telephone line to request checks on vulnerable neighbors and friends. The Department of Human Services and police responded to nearly 50 such requests by early Monday. The city’s Department of Aging also telephoned more than 300 senior citizens to offer help, such as rides to cooling centers.

The Cook County medical examiner’s office reported two heat-related deaths in suburban Chicago on Monday. Both victims were men with heart disease, which contributed to their deaths along with heat stress. In Oklahoma, authorities reported two more deaths that happened over the weekend.

In Missouri, at least 14 deaths since July 12 are blamed on the heat after a 71-year-old woman died in St. Louis during the weekend, Brian Quinn, a spokesman for the Missouri Department of Health and Senior Services, said Monday.

In Wisconsin, sheriff’s deputies put a high priority on responding to calls about disabled vehicles. “When it’s 100 degrees and you’ve got kids in the car, that’s not good,” said Waukesha County Sheriff’s Lt. Thom Moerman.