NEW YORK — Forecasters warned of potentially dangerous temperatures from Minnesota to Massachusetts, as the nation’s largest heat wave of the summer stretched out and stagnated, with relief in many places still days away.

The National Weather Service says most states in the U.S. were expected to have some areas where the temperature would hit 90 degrees or more on Wednesday. Humid air made things feel worse, with heat indexes in some places over 100.

In New York City, sidewalk food vendor Ahmad Qayumi said the space inside his steel cart got so hot, he had to turn off his grill because he couldn’t breathe.

Amid the heat, officials in Maryland worked to keep a failing pipe from cutting off water to hundreds of thousands of people, just when they needed it most.