Highs reached from the low to upper 90s Monday with heat index values in the upper 90s to lower 100s.
The National Weather Service on Monday afternoon issued a heat advisory for Tuesday, meaning that the heat index could reach from 105 degrees to 110 degrees. Temperatures were forecast to reach the upper 90s, the NWS said.
An excessive-heat watch was also issued for Wednesday when temperatures were forecast for 98 degrees to 102 degrees. Heat index values could reach up to 110 or higher in eastern parts of the state.
Heat index values are based on dew-point levels -- the amount of moisture in the atmosphere. The higher the dew point, the hotter it feels.
Public health officials were most concerned about the elderly and very young, but they cautioned that everyone needs to take it easy for the next few days.
"People need to be cautious no matter what age they are," said Dr. Marcus Plescia, chief of chronic disease and injury at the state Department of Health and Human Services. "We also worry about people who work outdoors. They need to take frequent breaks and they particularly need to drink plenty of fluids."
Plescia recommended that people without air conditioning at home spend time at shopping malls or libraries. Other recommendations include:
Kelly Stewart, 23, of Benson was relying on her fan to keep her cool as she sold watermelon from a booth at the State Farmers Market in Raleigh.
"That's about all you can do, and plenty of liquid," Stewart said. "And watermelons. Watermelon helps."
The heat wave has been moving across the country for several days. From Michigan to Oklahoma, the upper Midwest and Plains had numerous heat warnings Monday with temperatures expected to climb into the 90s or 100s, and spark thunderstorms.
Progress Energy anticipated near-record or record demand for electricity as temperatures rise this week, but the utility didn't anticipate problems meeting that demand, said spokesman Mike Hughes. The company's previous demand record was set on July 27, 2005, between 4 p.m. and 5 p.m., Hughes said.