Heat, humidity to rise this week on Long Island, as National Weather Service urges 'extreme caution'

Though Long Island, with its cooling ocean effects, figures to escape much of the unbearable heat wave embracing parts of the nation this week, don’t think that means we’ve got it made in the shade.

The National Weather Service said the heat index, the scale that calculates how the combination of temperature and humidity feels to the human body — the so-called “real feel” temperature — should soar into the “extreme caution” zone later this week, a designation that warns of factors that can lead to heat exhaustion and heat stroke.

“We’re looking at this heat from the west and how it is going to get into the area,” weather service meteorologist Jim Connolly said. “The spillover effect is how it happens, the heat building across the west, in the interior, the air masses migrating"

Because of the cooling effects of the ocean, Connolly said, "generally speaking, we don’t get into a real dangerous danger zone." 

But, he added, "I wouldn’t be surprised if by Thursday or Friday we’ll put out a heat advisory, warning of an increased risk of heat injuries.”

The Town of Hempstead is set to open multiple cooling locations from 9 a.m. to 4 p.m. beginning Wednesday and continuing through Saturday. The exact locations were being finalized late Monday and will be announced at a news conference in East Meadow Tuesday, officials said.

The town is also extending beach hours until 7 p.m. and hours at municipal town pools through 8 p.m., officials said.

While Long Islanders won't get the searing 118-degree temperatures recorded in places like Phoenix and Las Vegas, the weather service said Nassau and Suffolk could see temperatures well into the mid-90s by week’s end — with the heat index over 100.

That is an area of “extreme caution,” according to the weather service — a zone where the combination of heat and humidity make “heat stroke, heat cramps or heat exhaustion possible with prolonged exposure and / or physical activity.”

The heat index has four real-feel categories: caution, when it feels like it’s between 80 and 90 degrees; extreme caution, when it feels like it’s between 90 and 103; danger, when it feels like it’s between 103 and 124; and, extreme danger, when it feels like it’s 125 degrees or higher. The final category indicates heat stroke is “highly likely,” the weather service said on it’s website.

In explaining the effects of heat and humidity on the human body, the weather service said that while the adage suggests “It’s not the heat, it’s the humidity,” in reality “it’s both.”

“When the body gets too hot,” the weather service said in its online explanation, “it begins to perspire or sweat to cool itself off. If the perspiration is not able to evaporate, the body cannot regulate its temperature. Evaporation is a cooling process.”

While Thursday and Friday are expected to have a heat index topping 100, chances are most of the week will not see temperatures over 90, with “real-feel” temperatures out of the danger zone. And, even though temperatures should be in the low to mid-90s late in the week, which will likely trigger warnings on limiting strenuous outdoor activities, Connolly said we’re in for mostly sunny skies — and fine seasonal weather.

“When it gets like that,” he said, “go to the beach.”

By John Valenti

john.valenti@newsday.com

John Valenti, a reporter at Newsday since 1981, has been honored nationally by the Associated Press and Society of the Silurians for investigative, enterprise and breaking news reporting, as well as column writing, and is the author of “Swee'pea,” a book about former New York playground basketball star Lloyd Daniels. Valenti is featured in the Emmy Award-winning ESPN 30-for-30 film “Big Shot.”