Extreme warning issued to millions as ‘steam cooker’ heatwave turns 25 states into a sauna

Nearly 200 million Americans are suffering through another stretch of extreme heat and humidity this week, which experts warn could turn deadly within minutes.

Extreme heat warnings have been issued in several states throughout the Upper Midwest and Northeast, including New Jersey, Pennsylvania, Minnesota, Wisconsin, North Dakota, Wyoming, Montana and Michigan. 

In major cities near the Canadian border, such as Minneapolis, Milwaukee and Fargo, temperatures in July typically hover in the low 80s.

However, forecasts warn that the heat index values, or ‘feels like’ temperatures, will soar to between 100 and 110105°F  through Thursday.

Overall, 25 states from Nebraska to Maine have been warned to stay indoors and avoid strenuous activity as a massive dome of high pressure in the atmosphere has turned the US into a ‘steam cooker’ of hot and moist air.

AccuWeather Meteorologist Brandon Buckingham said: ‘It is recommended that residents, who are able, remain indoors during peak heating hours, early this week.’

‘If you have to be outside, consider taking numerous breaks, utilizing shaded areas, wearing light-colored clothing and staying hydrated,’ he added in a statement.

Health experts have warned that extremely humid weather can make it more difficult to sweat and cool the body down naturally, potentially leading to life-threatening conditions like heat stroke within a few minutes of being outside.

The National Weather Service (NWS) has also issued heat advisories throughout the Northeast and New England, in New York, Massachusetts, Rhode Island, Delaware, Vermont, New Hampshire and Maine.

A heat advisory is issued when the combination of heat and humidity is expected to make it feel like 95 to 99°F for two or more straight days, or between 100 and 104°F on any single day. This buildup of hot and sticky air is expected to last through at least Wednesday.

The steam cooker conditions have been caused by a large ‘heat dome’ sitting over the central US. These domes are large, high-pressure systems that trap hot air near the ground, acting like the lid on a boiling pot.

The humidity is the real danger during this widespread heatwave, with dew points expected to reach the ‘very humid and uncomfortable’ range for many people over the next three days.

Dew points are a measure of moisture in the air, with higher readings meaning the air is sticky and heavy, creating a ‘steaming’ heat that can be dangerous to human health.

Low and normal dew points usually sit in the 40s and 50s°F, making the air dry and comfortable. However, this week’s dew points are expected to approach 70°F, making it feel hotter and more oppressive when outdoors.

Dr Omer Awan of the University of Maryland School of Medicine told the Daily Mail: ‘The more humid it is, the less likely we are to sweat, and then that can make us more prone to heat-related illnesses as well.’

‘All these things can happen not in hours, but in minutes if you’re exposed to extreme heat outside.’

The NWS has urged elderly adults, children and those with chronic health issues to stay indoors and use air conditioning, as they are the most at risk for heat-related illnesses.

Heat exhaustion often starts with heavy sweating, fatigue, developing cool, pale, clammy skin and a fast, weak pulse, muscle cramps, dizziness, nausea and headaches.

As for heat stroke, which is far more deadly and can develop within 15 minutes in extreme conditions, the first symptoms are often a throbbing headache, confusion, slurred speech, nausea, dizziness, and a fever above 103°F.

‘Heat stroke is a medical emergency. That is when not only do you have the symptoms that I described, but you start to feel confused, you start to feel agitated, you’re not aware or oriented,’ Dr Awan noted.

Awan added that in extreme cases, heat stroke sufferers may experience seizures and fall into a coma, leading to death.

AccuWeather noted that this week’s steam cooker heatwave will only be slightly less intense than the massive scorcher across the US in the first week of July.

Dew points leading up to the Fourth of July hovered near 80°F, meaning the air was closer to tropical conditions and felt like a sauna to many.

Temperatures also soared to over 110°F in multiple areas along the East Coast.

Despite the slightly lower temperatures, NWS officials are still warning the public to stay hydrated, limit time in the sun during the peak sunlight hours and use air conditioning whenever possible.

‘Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes,’ NWS warned.