(CNN) — A heat wave seared the eastern United States Tuesday, with the heat index expected to reach 100 degrees or more, forecasters said.
At noon, New York's heat index was 96 degrees, well on a pace to touch triple digits later in the day, said CNN meteorologist Chad Myers. Heat indices represent how hot the weather feels, based on the actual temperature and humidity.
"I was in New York City last week: it's so much more than the heat, it's the humidity sticking around. You walk around the city and it feels like 102 and it's brutal," Myers said.
The heat indices for the Northeast, Mid-Atlantic and Midwest are expected to soar well past 100 degrees Tuesday, the National Weather Service said. A heat advisory was in effect for parts of Massachusetts, Connecticut and Rhode Island, as well as much of Michigan.
It's enough to make pedestrians run to the shady side of the street.
"I looked across the street: which side is the sun shining on and which side is the shade," Randy Turner told CNN affiliate WCBS.
"I was just thinking, walking down the street, why am I walking in this heat?" Michelle Sangenito also told WCBS.
People were willing to hit the floor just to beat the heat.
"Well, I came home late last night to a couple roommates just, like, laying out. I chose the ground because that's cooler," Holly King told CNN affiliate WABC.
Volunteer emergency medical technician Mark Sanders was standing vigil among the 60,000 visitors in Central Park. "We are on alert for heat emergencies. We do have a lot of water, a lot of fluids and cooling capabilities," he told WABC.
Rain, however, will cool the eastern third of the country by the weekend and bring pleasant weather to that region next week, with temperatures reaching only 80 degrees, Myers said.
But the rain also will bring the potential for hail and high winds in the northeast on Thursday, Friday and Saturday, Myers said.
Elsewhere in the country, a wacky weather pattern will bring rain and possible flash flooding to the South and Southwest, forecasters said.
Flood watches are posted in Texas, New Mexico, Colorado and Arizona, and the rainfall will bring temperatures 20 degrees below average, CNN meteorologists said.
The wetness will bring relief to drought-wracked Texas, but flooding is a concern this entire week, Myers said.
"There's a potential for heavy downpours in dry washes," Myers said.
Meanwhile, "monsoonal moisture will increase across the southern High Plains, with flash flooding possible," the National Weather Service said.
"The rain and extensive cloud cover will also keep temperatures across the region quite cool for this time of the year, with some areas over 20 degrees below their average July temperatures" in parts of west Texas, Arizona and New Mexico.