Nearly 250 million Americans face 90-degree temps as dangerous heat wave moves east

A summer heat wave has 245 million Americans facing 90-degree temperatures - with 30 million looking at triple-digits - as the system moves east.

Heat records dating back 250 years are set to fall across the nation thanks to the prolonged wave that experts advise can have deadly impacts.

"Be careful with doing new activities that can get you dehydrated quickly, so acclimate to the heat and don’t go out during the warmest parts of the day," Mayo Clinic Dr. Jesse Bracamonte said. "Try to find the coolest parts of the day to keep yourself healthy and away from heat-related illness."

AccuWeather forecasters say the heat wave will impact much of the eastern US between Sunday and Wednesday. More than 245 million people will experience 90-degree temperatures during the stretch. For many, high humidity will add to the miserable feeling making it feel hotter than the thermostat says.

Mid-July typically tends to be the hottest time of the year for many places, but forecasters say the heat wave will bring above-average temps to many cities.

"In some cases, such as in Charlotte and Raleigh, North Carolina, daily record highs dating back to the 1800s will be challenged on multiple days in the coming week as afternoon temperatures hover near the 100-degree mark," AccuWeather Senior Meteorologist Reneé Duff said.

This summer, the US has already had numerous daily high-temperature records fall as climate change continues to make an impact across the world.

On Saturday, the high temperature in New York City is only expected to reach 84. Then it is set to jump to 91 on Sunday and remain in the 90s until Thursday.

In Washington, DC, the high is expected to reach 93 on Saturday and hit a whopping 101 degrees on Tuesday.

In St. Louis, temperatures are expected to approach 90 degrees on Saturday before hitting the upper 90s on Sunday and Monday.

Las Vegas has already seen scorching temperatures through much of the summer and the high will approach 110 degrees on Saturday. Then, it is expected to hover at that mark throughout the week.

Forecasters and medical professionals are warning people about the deadly potential of the historic highs. Dr. Erick Shessler, of Dartmouth Health Children’s Hospital, toldWMUR that anyone can be impacted by heat-related illness.

Those who work outside, children and older Americans face the biggest risks from high temperatures.

“We’re noticing excessive sweating, you’re getting particularly thirsty. You’re starting to get tired when you don’t expect to, maybe a little bit more winded, maybe nauseous, for example. If we’re starting to see some of those symptoms, we got to be paying attention,” Shessler told the outlet.

Many will head to the beach or pool to cool off, but Schessler said spending too much time in the sun can be problematic.

“Libraries, museums. Sometimes on those really hottest of days, it sounds tempting to go to the beach, but occasionally you want to build in some of those little breaks, get inside, get some AC, get some cooler temperatures for you,” he said.