5 Numbers to Know About the Approaching Heat Wave

Millions of Americans from Texas to Maine will experience sweltering conditions this week as a heat wave hits the eastern half of the United States, meteorologists said. Starting Sunday, rising temperatures will hit the South, then extend across the Midwest and spread to the East Coast by mid-week.

It’s not officially summer yet, so the real baking season is yet to come. But this earlier spell of muggy weather, and the fact that it is expected to last for days, could be shocking for many regions.

Here are five numbers to put this coming heat wave – and our warming climate – into context.

99

The expected high temperature in Fahrenheit Wednesday in Pittsburgh. It would be the highest ever recorded there in the month of June, said Josh Weiss, a meteorologist with the National Weather Service’s Weather Prediction Center. (In Pittsburgh, he added, there are temperature records going back to 1875.)

That figure could be just one of what Mr. Weiss says is dozens of temperature records broken this week in cities across the northeastern United States. On Monday, he said, about 20 daily record temperatures are forecast for the Ohio Valley.

And from Tuesday to Thursday, he said, as many as 75 record highs are expected — both daily and for the month — as the heat wave moves through the Mid-Atlantic and into New England. In many of those places, temperatures are expected to reach above 95 degrees sometime in the middle of the week.

22.6 million

Figures show the number of people across the country who were under extreme heat advisories, watches or warnings on Saturday the National Weather ServiceThat’s approximately the population of the state of Florida.

While experts say this doesn’t include everyone who will be affected by this heatwave, it does give some idea of ​​the scale of its impact. In other words, even if you don’t live somewhere with an extreme heat warning, it’s worth being cautious.

The heat wave “is going to hit some densely populated areas that haven’t had as many extreme heat stories recently,” said Daniel Swain, a climate scientist at the University of California, Los Angeles. “Now it’s New England’s turn.”

12

The number of consecutive months in which the average temperature on Earth has been the highest ever recorded for that month. Last month was hottest May ever. In June, that number could reach 13.

“At this point it is almost trivial to say that climate change has intensified heat waves like the one about to happen,” said Dr. Swain.

1,220

The estimated number of deaths per year due to extreme heat, according to the Center for Disease Control and Prevention. That makes heat the deadliest type of extreme weather. (Causing floods, on the other hand about 98 deaths per year.) But that number may be an undercount because heat deaths are difficult to track because heat can worsen underlying conditions. And it tends to be most dangerous for people who are already vulnerable, such as older Americans who don’t have air conditioning.

Scientists and health experts say they hope that by treating extreme heat a little more like any other type of natural disaster, people will take more steps to prepare for it.

4

The highest number on a new scale created by the National Weather Service and the CDC that measures weather conditions health risks associated with extreme heat in a specific location on a specific day. Because as anyone who’s spent summer days in Houston or Phoenix can tell you, not all heat feels the same. Experts say even slightly cooler temperatures combined with high humidity can be more dangerous.

The shell, called Heat riskuses CDC data to take into account how unusual the heat is for the time of year, the duration of a heat wave and whether the temperature poses an increased risk to an area.

For Monday, meteorologists have put parts of central Iowa, western Illinois and Missouri (including Kansas City) at a 4, the most extreme risk level. At that level, the entire population is at risk, emergency room visits are likely to increase significantly and the heat could be deadly for the most vulnerable. As the heat wave spreads, the risks will be high in cities like Chicago, Cleveland and Buffalo.

According to meteorologist Weiss, the new instrument will hopefully help people understand that heat hazards can be exacerbated by numerous factors.

This week’s heat wave, for example, could last into next weekend in parts of the Northeast, where residents aren’t used to or prepared for temperatures above 90 degrees Fahrenheit — especially in mid-June. And because meteorologists say the heat wave will persist and the nighttime will offer no respite, the risk of health effects is much greater.

“There is no relief, so we are going to have a build-up of heat stress during this heat wave,” Mr Weiss said.

Austyn Gaffney contributed to the reporting.