Grim warnings are issued as oppressive heat wave in US shows no signs of slowing

The scorching heat that has already settled across much of the south-central US and prompted heat warnings and advisories across the region is now beginning to extend into the Northeast Wednesday, bringing “steamy temperatures into the 90s” and heat index values — in other words, how hot it will actually feel, based on both the air temperature and humidity — that are even higher, according to the Weather Prediction Center.

Boston Mayor Michelle Wu declared a heat emergency through Thursday and announced there will be at least a dozen cooling centers at facilities across the city and more than 50 splash pads at parks and playgrounds. “It is clear that a changing climate is a risk to our health,” the mayor said.

A heat advisory is in effect Wednesday morning through 8 p.m., and the heat index is forecast to soar past 100 degrees, according to the National Weather Service in Boston.

Connecticut’s governor activated the state’s extreme hot weather protocol through Sunday which will help, in part, ensure the availability of cooling centers.

At least one-third of the US population is under heat advisories and excessive heat warnings and roughly 265 million people will see temperatures above 90 degrees in the coming days — with some of the highest temperatures forecast over the southern Plains.

In Texas, some prisons are without air conditioning

Oklahoma and Texas saw some of the highest temperatures in the region Tuesday — with a record high 115 degrees recorded in Wichita Falls, Texas.

But a number of incarceration facilities across the state do not have working air conditioning, the Texas Department of Criminal Justice said.

“There are 100 (Texas Department of Criminal Justice) units, 31 have full AC, 55 have partial AC, and 14 have no AC. We take numerous precautions to lessen the effects of hot temperatures for those incarcerated within our facilities,” Amanda Hernandez, a spokesperson for the department, told CNN In an email.

“In 2022, there have been seven inmates who required medical care beyond first aid for heat related injuries, ” Hernandez said. “None were fatal.”

The Electric Reliability Council of Texas (ERCOT), the organization that operates much of the state’s electric grid, set another unofficial record for demand Tuesday, a spokesperson told CNN. Another record is expected Wednesday.

Why heat and humidity are especially dangerous

Heat is one of the top weather-related causes of death in the US, according to Kimberly McMahon, public weather services program manager with the National Weather Service.

“Heat affects everyone by limiting the body’s ability to cool down,” McMahon said.

High humidity levels only further limit that ability.

“Sweating removes 22% of excess body heat by redirecting heat towards the evaporation of the sweat,” CNN meteorologist Robert Shackelford said. “High humidity means that there is more moisture in the air. Since there is significantly more moisture in the air, it causes sweat to evaporate slower, which leads to a slowing down of your body’s natural ability to cool. That is why heat indices on a day with high humidity can feel significantly hotter than the actual temperature of the air.”

Too much heat and humidity can lead to heat-related illnesses including heat cramps, a heat rash, heat exhaustion “and — the worst of all — heat stroke which can result in death,” McMahon said.

“Extreme heat is a real threat and needs to be taken seriously,” McMahon added.