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Downpours flood portions of Douglas Ave., in North Providence, Rhode Island, on Monday.
CNN  — 

A “perfect storm” is unfolding this summer, one climate scientist told CNN, as atmospheric ingredients combine to create deadly flooding in the Northeast US and record-breaking heat in the Southwest US and around the world.

Deadly flooding inundated parts of the Northeast, trapping people in their homes and killing at least one woman who was swept away by the fast-moving water. Rivers in Vermont rose quickly in the torrential rain on Monday to levels not seen since Hurricane Irene in 2011.

On Sunday, more than 7.5 inches of rain fell at West Point, New York, in just six hours — a 1,000-year rainfall event for the area, according to a CNN analysis of data from the National Oceanic and Atmospheric Administration. A 1,000-year rainfall event is one that is so intense, it only happens on average once every 1,000 years.

The climate crisis is stacking the deck in favor of more intense weather events like the heavy rain and flooding in the Northeast, said Michael E. Mann, a climate scientist and distinguished professor at the University of Pennsylvania.

“Sure, weather is weather. It’s going to happen — rainfall, flooding events are going to happen,” Mann told CNN. “What climate change is doing is it’s supercharging them, so when you get one of those weather systems that’s producing large amounts of rainfall, you get more rainfall.”

There’s another, more surprising way that the climate crisis could be driving these extreme rainfall events, Mann said, and it’s something on the forefront of climate research: The jet stream could be getting “stuck” in positions that prolong these kinds of extreme events.

The jet stream is the fast-moving river of air high in the atmosphere that ushers weather systems across the globe. Importantly, it’s fueled by the extreme difference in temperature between the equator and the poles.

But the planet is not warming equally in all locations, Mann explained. The Arctic is warming much faster than the Lower 48, for example, which “reduces the temperature difference from the equator to the pole.”

Scientists suspect that this decrease in temperature difference is changing how the jet stream behaves.

“The jet stream basically stalls and those weather patterns remain in place — those high and low pressure centers remain in place,” Mann said. “And we’re seeing more of these sort of stuck, wavy jet stream patterns that are associated with these very persistent weather extremes, whether it’s the heat, drought, wildfire or the flooding events.”

Joel Angel Juarez/The Republic/USA Today Network
A person walks along Roosevelt Row in Phoenix on July 5. High temperatures there could stay north of 110 degrees through this week.

As the Northeast is inundated with flooding rain, dangerous heat is threatening other parts of the world. Temperatures are soaring in the Southwest this week, where Phoenix could break its record for consecutive number of days above 110 degrees.

Last week, the planet’s average daily temperature climbed to record levels in data tracked by two climate agencies in the US and Europe. Climate scientists told CNN that the global temperatures were likely the highest in at least 100,000 years.

Meanwhile, the EU’s Copernicus Climate Change Service found that last month was the hottest June by a “substantial margin” above the previous record, which was set in 2019.

Given the exceptional heat, scientists are concerned that 2023 could be the hottest year on record.

Mann said that El Niño is “adding extra heat, extra fuel to the fire.” El Niño, which is a warm phenomenon in the Pacific Ocean, is combining with the climate crisis “and what you get is new record levels of heat at the planetary scale.”

But Mann said without the climate crisis, which is caused by burning fossil fuels, “we simply wouldn’t be seeing these extreme events.”

“Those are conspiring. They’re combining,” Mann said. “The steady warming combined with an El Niño; extreme weather events related to those changing jet stream conditions – it all comes together, if you will, in a perfect storm of consequences, which translates to truly devastating and deadly weather extremes that we’re dealing with here right now.”

CNN’s Rachel Ramirez, Laura Paddison and Jennifer Gray contributed to this story.