Some 195 million Americans — out of a population of more than 330 million — are facing dangerously high temperatures as much of the mainland U.S. is under excessive heat advisories beginning Thursday and expected to last until the weekend.

Before relief arrives, temperatures will reach levels that feel hotter than 100 degrees Fahrenheit, the National Weather Service warns.

Earlier this summer, a heat wave around the Portland, Ore., area and in Canada was blamed for the death of hundreds of people. This time around the oppressive heat will not only exacerbate drought conditions and wildfires in the West but also will make for dangerous conditions on the East Coast.

The National Weather Service predicts the Interstate 95 corridor in the East could reach 100 F Thursday afternoon. Oppressive heat indexes, a measure of how hot it really feels outside, are expected to range between 105 to 110 degrees Fahrenheit.

Dew points, a measure of the amount of moisture in the air, could reach as high as 80 in the Boston area. That's a number that is "basically record territory" for New England, according to WBUR, Boston's NPR news station. Some parts of Massachusetts could reach a heat index of 110.

Several states have opened cooling centers for residents to stay safe in the heat.

In the Pacific Northwest, temperatures could hit 105 F on Thursday, according to earlier predictions by the National Weather Service in Portland. Just over a month ago temperatures skyrocketed to a record 116 F.

By Friday, the "worst-case scenario" has the region reaching as high as 111 F in some parts of western Oregon before finally cooling down over the weekend, according to the National Weather Service in Portland.

These conditions all come just days after climate scientists released a major report examining how fast the climate is warming, showing heat waves, extreme rain and intense droughts are on the rise.

The scientists say heat waves are more frequent and intense and droughts are getting hotter and drier — events linked to the human influence on the climate.

Intense storms will follow the heat

In the Washington, D.C. area, hot and humid weather this week brought damaging thunderstorms in the late afternoon. High winds downed trees and wires in Virginia, Maryland and Washington. A bolt of lightning set a Germantown, Md., apartment complex on fire, reportedly displacing at least 25 people.

Similarly damaging thunderstorms may arrive for the Midwest and elsewhere along the East Coast on Thursday and Friday, the National Weather Service says.

Thunderstorms are expected to form and move across parts of northeast Kansas, northern Missouri and north-central Illinois, the National Weather Service predicts.

The Great Lakes region is most at risk for those severe storms on Thursday, according to the weather service. Damaging winds, hail and even tornadoes could also occur.

How to stay safe in dangerous heat

Extreme heat is considered the most dangerous type of severe-weather event in the U.S. as our body's ability to cool itself is challenged.

Here are some tips to stay cool and safe:

• It's recommended that people reduce or reschedule strenuous activities until it's cooler.

• Children, babies, older adults and others with chronic medical conditions should stay in the coolest place possible as they are especially vulnerable to heat-related illness or death.
  
• Monitor for signs of heat cramps, heat exhaustion or heatstroke and know what to do if you see someone suffering from any of those illnesses

• Dress in cool, light-colored clothing. Drink plenty of water and nonalcoholic drinks even when not feeling thirsty.
  
• When using a fan, don't direct the flow of the fans directly toward yourself if the room is hotter than 90 F. The dry air will dehydrate you faster.
  
• No air conditioning or fans at home? Head to your area's nearest cooling center or library to keep cool.

Sitting still on the couch and re-upping this TV streaming guide from March 2020 could be the safest choice this week.