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‘Bomb cyclone’ hits the northern US: What is this storm?

Reports suggested that around 27,000 customers were without power on Tuesday morning, more than a third of them in Michigan. More than 9,000 flights were delayed, and 889 were cancelled within, into or out of the US

Fresh snow blows through Lowville, New York, on Monday. (Photo: AP)

3 min readNew DelhiDec 31, 2025 07:00 PM IST First published on: Dec 31, 2025 at 07:00 PM IST

A powerful “bomb cyclone” barreled across the northern United States on Monday (December 29), triggering severe winter weather in the Midwest and the East Coast. Blizzard conditions with frigid temperatures, cold air, strong winds, and snow led to treacherous travel amid the busy holiday period.

Reports suggested that around 27,000 customers were without power on Tuesday morning, more than a third of them in Michigan. More than 9,000 flights were delayed, and 889 were cancelled within, into or out of the US.

Forecasters expected the storm to intensify in the coming days, propelled by the clash of cold Canadian air and the warmth of the southern US.

Here is a look at what a bomb cyclone is, and why it can create dangerous conditions.

What is a bomb cyclone?

Storms typically form when a mass of low-pressure air meets a high-pressure mass. The air flows from high pressure to low, creating winds.

What defines a bomb cyclone is how rapidly the pressure drops in the low-pressure mass, by at least 24 millibars in 24 hours. This quickly increases the pressure difference, or gradient, between the two air masses, therefore making the winds stronger. This process of rapid intensification has an even more ferocious-sounding name: bombogenesis.

“Storms that undergo bombogenesis are among the most violent weather systems that affect a broad area. This is because the rapidly ascending air near the centre of the storm must be replaced by air surrounding the storm. As these winds move toward the centre of the storm at high speed, property damage can occur, trees may fall, and the power may go out,” according to a report by AccuWeather.

Bomb cyclones can happen in any season in the US. However, they primarily occur during fall and winter when frigid air from the Arctic can creep south and clash with warmer air masses.

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Where do bomb cyclones usually occur?

Bomb cyclones most commonly originate western North Atlantic. That is because it is a region where cold air from North America clashes with warm air over the Atlantic Ocean, leading to bombogenesis. Festering storms can also be fueled by the warm waters of the Gulf Stream.

A 2021 study by Northern Illinois University revealed that around 7% of all nontropical low-pressure systems near North America from 1979 to 2019 were bomb cyclones. This means that, on average, around 18 bomb cyclones occurred per year near North America in those 40 years.

Why are bomb cyclones dangerous?

Winds during a bomb cyclone can reach speeds of up to 80 kmph. They knock down trees, disrupt electricity supply, and lead to lakeshore flooding.

Precipitation, including snowfall, can also be intense. Blizzard conditions can take place, sometimes accompanied by lightning as the system intensifies.