WHOI scientist on possible trends

In August 2023, as strong winds tore through her South Shore town during a summer storm, climate scientist Sarah Das did something she’d never done in more than 20 years living in Massachusetts: she took her daughter and their dog into the cellar.

She’d received an urgent tornado warning, and waited in the dank underbelly of her antique home until the all clear. Nothing touched down in her town, but “quite a number were reported from the same storm nearby. Even made the national news,” she said.

The memory stuck.

Fast forward to Sept. 6, 2025, when five tornadoes struck Massachusetts — the most in one day since 2011 — raising the increasingly pressing question: are tornadoes becoming more frequent here?

The five tornadoes were all west of Boston. But Cape Cod has been hit as well in recent years.

“It’s a reasonable question,” said Das, a Woods Hole Oceanographic Institution researcher and member of Science Moms, a group of scientist parents working to make climate science accessible and to press for solutions.

Massachusetts averages about two tornadoes per year, though some years have more, some less. But with five at once, it’s natural to ask whether climate change plays a role, she said.

Tornado tracking is tricky

Despite the recent cluster, Das said the science hasn’t yet showed a clear trend directly connecting tornado frequency in the region to climate change. Moreover, “there isn’t even necessarily a clear signal that tornadoes have increased” overall, she said. Only more data collection, over time, will tell.

Part of the challenge lies in the data itself. Tornado records in the U.S. only go back to 1950, and storm detection and reporting methods have changed dramatically since.

“You’re not comparing apples to apples if you’re looking at how many tornadoes there were in the ’50s or ’60s versus recently,” Das said.

Improved radar, cell phone videos, and more public awareness may be leading to a rise in reported and confirmed tornadoes — especially weaker ones.

Since 2007, scientists have used the Enhanced Fujita Scale to rate tornadoes. The original Fujita Scale from the 1970s rated the wind storms from F0 to F5 based on how much damage they did. The enhanced scale uses updated wind speeds and more detailed damage signs for a more accurate picture of tornado strength.

The tornadoes that touched down in Massachusetts earlier this month, Das said, were EF1, “which is still destructive if it hits your house or your trees.”

A closer look: the tornadoes of Sept. 6, 2025

On Sept. 6, five EF1 tornadoes touched down in four Massachusetts towns, all within half an hour, with wind speeds ranging from 94 to 104 miles per hour, according to the National Weather Service.

Paxton charted two of the storms, one with 100 mph winds, the other 94 mph, the weather service reported. Holden, Berlin and Stow each saw a tornado with 104 mph winds.

How a changing climate creates favorable conditions

While Das made clear that tornado trends remain inconclusive, she emphasized that climate trends overall are much clearer — and that matters when assessing tornado potential.

“The atmosphere and the ocean are warming,” she said, noting the Gulf of Maine, which encompasses both Cape Cod Bay and Massachusetts Bay, “is one of the fastest warming areas of the ocean on the planet.”

“That leads to increased moisture and instability in the atmosphere, which are two of the main factors needed for tornado formation within a convective storm like a thunderstorm,” she said.

So, even if tornadoes themselves haven’t been increasing in number in a measurable way, the ingredients for their formation — warm, moist, unstable air — are. Das also noted changes in when tornado-generating thunderstorms occur, starting sooner and extending further into the year.

“We always thought it was a summer phenomenon. But winters are getting warmer, in particular in the Northeast, and there are thunderstorms now in the winter,” she said, “which means the seasonality of tornadoes could be expanding, and we may be caught off guard.”

More tornado reports on Cape Cod

While much of Massachusetts is no stranger to severe storms, verified tornadoes have historically been rare on Cape Cod and the Islands. That’s changed in recent years.

While researchers like Das can’t say for certain whether that’s because of better monitoring and reporting, or the influence of climate change, or both, the region is surrounded by those all-important warming waters, meaning it is increasingly as likely to see tornadoes here as places further inland.

Over nearly 30 years, from 1951 to 1977, only three verified tornadoes were recorded on the Cape and Islands. But more recently, during a span of just three years — 2018 and 2021 — five tornadoes were confirmed, according to the National Weather Service.

These included an EF0 tornado in Dennis in August 2021, a remnant of Hurricane Ida, and a 2019 cluster that spun through Harwich, Barnstable and Yarmouth, with storms also in Mashpee and Chatham. A more recent EF0 tornado damaged parts of Marstons Mills in 2023.

But those figures don’t include waterspouts — tornado-like vortices that form over water — which Das said she has personally witnessed. Their omission means the region may experience more storm activity capable of producing rotating winds than the official record reflects.

A need to be prepared

Tornadoes have now been reported in nearly every part of the state, including areas — like Cape Cod — previously considered to be at low risk. Das believes that even without clear long-term trends, towns as well as home- and business owners should consider being more proactive in preparing.

“I think it’s good for people to be learning and be aware that it could happen at any time,” she said.

Back at her own home, Das hasn’t yet had to retreat to her cellar again, but she hasn’t forgotten what it felt like. That day, she said, “I realized while we were sitting there, ‘it’s not very comfortable. I wish we had some chairs and maybe a book and more water.’”

Now, she keeps a few essentials tucked away down there, just in case the next warning isn’t a false alarm.

Heather McCarron, hmccarron@capecodonline.com, writes about climate change, environment, energy, science and the natural world.

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