A weather pattern parked near Bermuda is helping fuel an unusual burst of heat across New York and much of the eastern United States this week, sending temperatures soaring well above normal for May and pushing some cities close to record territory.
The setup, known to meteorologists as the Bermuda High, is a large area of high pressure over the Atlantic Ocean that often shapes summer weather patterns across the East Coast.
When it strengthens or shifts westward, it can funnel warm, humid air northward into the eastern U.S. That’s exactly what’s happening now.
“An early-season heatwave is in full swing across the eastern U.S.,” the Weather Prediction Center wrote in the short range forecast discussion. “A Bermuda High anchored over the western Atlantic will continue to bring a long fetch of warm southerly flow across the eastern half of the country, with high temperatures reaching into the mid-90s during the next couple of days. These temperatures will challenge or break temperature records across the east-central U.S. including the Mid-Atlantic, spreading into New England this afternoon.”
While a cold front pushes through the Plains late Tuesday into early Wednesday, the East Coast is expected to stay locked in a stretch of unusually hot weather for several more days. Temperatures from the Mid-Atlantic southward are forecast to remain in the upper 80s and 90s through at least the weekend.
Why weather near Bermuda matters
The heat is being fueled in part by the Bermuda High — a large, semi-permanent area of high pressure over the North Atlantic Ocean that plays a major role in shaping weather patterns across the eastern United States.
The system shifts position throughout the year. During summer and early fall, it typically expands westward and settles closer to Bermuda, which is where it gets its name. In winter and early spring, it is usually positioned farther east near the Azores and is often called the Azores High during this time period, according to the National Weather Service.
When the Bermuda High strengthens or expands westward, clockwise winds circulating around the system help pull warm, moisture-rich air northward from the Gulf of Mexico and Atlantic Ocean. That warm flow spreads across much of the eastern half of the country, driving temperatures higher while also increasing humidity levels, according to NOAA.
The pattern is especially noticeable this time of year because many parts of the East have not fully adjusted to sustained heat yet, increasing the risk of heat-related illnesses during one of the first major warm spells of the season.
This year, the contrast may feel even sharper after a cooler and more active winter pattern lingered well into spring across parts of the country, with repeated blasts of polar air, clipper systems and late-season snow events delaying more consistent warmth.
The Bermuda High doesn’t just make it hotter. It also pumps moisture into the atmosphere, which can help storms become stronger when weather systems move through.
And it can also play a significant role in hurricane season, helping steer storms across the Atlantic and sometimes pushing them away from or toward the U.S. depending on where it sits.
Why the heat wave feels so intense
It’s not just the temperatures making this heat feel miserable — it’s the humidity too.
The same weather pattern pulling heat into the East is also dragging in moisture from the Gulf and Atlantic, creating sticky conditions that can make it feel significantly hotter than the actual air temperature with feels-like temperatures nearing triple digits.
That’s especially true in major cities along the I-95 corridor, where concrete, asphalt and buildings trap heat well after sunset.
And unlike dry heat, humid air makes it harder for sweat to evaporate and cool the body naturally. When overnight temperatures stay warm too, there’s less opportunity for homes and cities to cool down before the next hot day begins.
How long will East Coast heat wave last?
The hottest conditions are expected through midweek before temperatures slowly ease in parts of the Northeast and Mid-Atlantic as a cold front moves east, according to the Weather Prediction Center.
Even so, much of the eastern U.S. is likely to remain warmer than average heading into the weekend, especially across the Southeast where humid air may linger longer behind the front.
Forecasters recommend limiting strenuous outdoor activity during the hottest parts of the afternoon, staying hydrated and checking on vulnerable neighbors during the early-season heat.
National heat index map: How hot does your city feel?
The map below identifies areas where the heat index is forecasted to reach NWS-defined levels from “Caution” (80 degrees Fahrenheit) to “Extreme Danger” (above 125 degrees).
The heat index measures how hot it actually feels when factoring for humidity. Prolonged exposure to a heat index above 80 degrees can lead to fatigue, as previously reported by USA TODAY. As it gets hotter, the risk continues to increase − potentially resulting in heat stroke or even death. Older adults, children, and outdoor workers are generally at higher risk of heat-related incidents.
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Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at baddison@gannett.com. Find her on Facebook here.
This article originally appeared on Rochester Democrat and Chronicle: Why New York is suddenly feeling summerlike heat in May
Reporting by Brandi D. Addison, USA TODAY NETWORK / Rochester Democrat and Chronicle
USA TODAY Network via Reuters Connect
