115-degree heat index? What the 'heat dome' means for your July 4th weekend

NEW YORK CITY - A stifling heat wave is settling over the New York City region, which will make the concrete jungle feel more like a steam bath for the next several days.

"Imagine you boil a pot of water, and you put the lid on top of it. That lid, that’s that heat dome building up. We’re underneath that lid, and the heat just kind of gathers up," FOX 5 Metrologist Mike Woods said to describe the oppressive weather pattern.

By the numbers:

The humidity is already making its presence known. Early Wednesday morning, temperatures were sitting at a sticky 75 degrees in Central Park and 72 degrees in White Plains. South winds blowing at 5 to 15 mph are consistently pumping up the heat and humidity, which is building underneath a massive ridge of high pressure extending from the Atlantic waters down into the southeastern states.

There was a brief moment of respite for some as an isolated thunderstorm cluster developed over the central and eastern sections of Long Island before swinging south. While this system is helping to clear the area and bring temporarily drier conditions, the potential for more isolated pop-up storms remains as the atmosphere destabilizes under the intense heat.

NYC forecast:

• Wednesday: Hot and humid with possible storms. High of 95 degrees
• Thursday: Very hot and humid. High of 102 degrees
• Friday: Very hot and humid. High of 103 degrees.
• Saturday (July 4th): Hot and humid with afternoon thunderstorms. High of 97 degrees.

Heat warnings

What we know:

An excessive heat warning officially goes into effect at noon Wednesday and will last until about 9 p.m. Friday.

While actual temperatures will peak around 95 degrees on Wednesday, the humidity will make it feel even hotter. For the next three days, heat index values are expected to skyrocket to 110–115 degrees.

By Friday evening, the warning will transition into an excessive heat watch, but it won't offer much of a reprieve. Heat index values are still expected to hover around 105 degrees for the city Friday night and Saturday.

July 4th impacts

What's next:

This extreme heat is part of a massive, life-threatening system baking over 230 million Americans leading up to America's 250th birthday this July 4th weekend.

FOX Weather reports that the last time NYC experienced back-to-back triple-digit days like the ones forecasted was over a decade ago, in 2011. While temperatures are expected to ease slightly by July 4th itself, the days leading up to the holiday will be brutal.

As New Yorkers prepare for the holiday weekend, extreme caution is advised. Health experts urge residents to stay hydrated, limit outdoor activities during peak heating hours, wear lightweight and light-colored clothing, and seek out air-conditioned spaces like malls or museums to escape the dangerous heat.