Another day of blistering heat covers U.S. (CBS News) NEW YORK - Millions of Americans endured yet another day of blistering heat. Temperatures in the 90s and even the 100s covered much of the country Saturday. At least 30 people have died from the heat, which the CDC says routinely kills more people than all other weather events combined. One doctor told CBS News that normally in heat waves, it's the elderly and the very young who are especially vulnerable. But she said a combination of factors now means everyone is at risk. Louisville, Kentucky was among the hottest spots in the country Saturday. The mercury there climbed to 108 degrees. It's a little stifling. I'm really glad there's air conditioning," said resident Debbie Barnhard. Triple digits spread across the Midwest, Northeast and mid-Atlantic. Extreme heat wave spreads across U.S. Midwest heat wave unwavering, moving east Chicago melts in heat wave of triple-digit temps Dr. Michelle Carter of Howard University Medical Center in D.C. recommends people stay inside air-conditioned buildings during heat waves like this one. She says the high humidity prevents sweat from evaporating off the skin, a process which normally helps cool the body. "So then the body doesn't have a way to get rid of that excessive heat, and then it's rapid rise internally in terms of heat," she said, "and that can affect quite a few of the major organs, specifically the brain and heart." In Washington, D.C., the temperature topped 100 by midday. The punishing heat sent tourists like Errin Gordon and her daughter, Madeleine, seeking relief indoors. Definitely her being out on the heat is hard on kids. So just going to go into the museums and stay out of it," she said. For others, like some residents in Charlotte, North Carolina, respite came in the form of donated air conditioning units. "It's a godsend," said one woman, "and I don't know how to say thank you." Meanwhile, some 200,000 people are still without power -- most in West Virginia after powerful storms hit there last week. As of Saturday night, many in those same areas are bracing for another round of severe weather expected to bring thunderstorms and strong winds