What is thunder snow? The strange weather phenomenon is sweeping through the East Coast and Midwest

On January 7, 2025By Littum

A rare weather phenomenon rumbled across several eastern and central US states this weekend as arctic air continues to bring heavy snow and freezing temperatures to millions of Americans.

Thundersnow, also known as a winter thunderstorm, occurs when a snowstorm is accompanied by thunder and lightning. As of Monday (Jan. 6) morning, the phenomenon has been reported across much of the southern Midwest, as well as in Maryland, Virginia and Washington, DC

The National Weather Service (NWS) in St. Louis, Missouri, shared satellite images taken by NASA’s GOES-East in space that showed lightning flashes across Arkansas, Kansas, Oklahoma and Missouri on Sunday (January 5).

“We’re getting sleet/thunderstorms,” NWS officials wrote in a post on X, formerly Twitter. “This just highlights that the snow/slush numbers are quite heavy – avoid travel if at all possible!”

The green spots on this satellite image are lightning flashes seen from GOES-East in space! That means…we’re getting thunder snow/thunder clouds! This just highlights that the snow/sud numbers are quite high – avoid traveling if at all possible! pic.twitter.com/8I9sSVfXVo5 January 2025

Meanwhile, footage of Kansas meteorologist Jim Cantore responding to the rare phenomenon has garnered thousands of views at the scene.

Thunderstorms in KC. We got it baby! Great day at the office! Live w/ @JimCantore on @weatherchannel pic.twitter.com/m1zJxwQdIl5 January 2025

What causes thunderstorms?

Thunderstorms occur when warm, moist air rises and condenses in cooler, drier air above it, forming towering cumulus clouds. Inside these clouds is a combination of light ice crystals, which float upward, and soft hail known as graupel, which is denser and falls downward. This causes both particles to knock into each other, causing electrons to be transferred from the ice crystals to the graupel. The end result is a cumulus cloud with positively charged ice crystals at the top and negatively charged graupel at the bottom, according to the National Oceanic and Atmospheric Administration (NOAA).

This builds up negative charge at the base of the cloud, repelling electrons in the ground below it. The charge difference between the cloud and the ground builds up until the potential energy is eventually discharged as lightning.

The energy from this impact heats the surrounding air, causing it to explode outwards and creating the rumbling sound we know as thunder.

Thunderstorms occur when this weather system occurs in the middle of a snowstorm.

Why is thunder snow so rare?

The conditions required to create thunderstorms rarely occur during the winter months.

“In winter (especially when the weather is cold enough for snow to fall), there is much less energy in the atmosphere and the heating of the surface is greatly reduced.” Jon Shonka Senior Scientist at the UK’s Met Office and researcher at the University of Reading, told LiveScience in an email. “Thunderstorms form more easily in the summer when the atmosphere is warmer and can contain more energy and moisture.”

On the rare occasions when thunder does occur, it tends to be around the Great Lakes. “In the United States, thunderstorms occur more frequently in the central part of the country, the Intermountain West and across the Great Lakes region,” Jesse Ferrelltold AccuWeather senior weather editor and meteorologist AccuWeather “Intense lake-effect snow bands, which have pockets of rapidly rising air due to the sharp contrast between cold air in the air and the warm lake water, often produce thunderstorms.”

However, FOX Weather Meteorologist Kendall Smith – who saw the phenomenon in Kansas City on Sunday – said it was very unusual to see the thunderstorms this far south, describing the event as “historic.”

Related: Polar vortex could bring deadly winter storms and the coldest weather in more than a decade to the US

The cold weather the US is currently experiencing has been driven by large-scale atmospheric pressure changes and a shift in the band of strong winds that normally hold cold air in the Arctic, known as the polar vortex. This shift causes freezing air to plunge much farther south than normal, resulting in the cold temperatures the United States is currently experiencing. And when this rush of freezing air bumps up against warmer, tropical air from the south, it can create the right conditions for thunder.

“A significant wave of moisture lifting from the Gulf of Mexico was ingested into the developing low pressure and was then lifted vertically to induce elevated instability.” Josh Weissa forecaster at NOAA’s Weather Prediction Center, told LiveScience in an email. “Where the atmospheric rise was most pronounced (usually on the north/northwest side of these intense cyclones), this resulted in an intense band of snow accompanied by lightning and thunder: thunder snow!”

Are thunderstorms dangerous?

“Like any storm that produces lightning, thunderstorms can be dangerous,” Weiss said. “However, the lightning and thunder that accompany a blizzard are usually less frequent and less intense than in summer thunderstorms.”

Unlike summer thunderstorms, where thunder can be heard for miles, snow tends to muffle the sound, limiting the distance at which it can be heard. Thus, people may be less cautious about an impending storm and more at risk of unexpected lightning strikes.

Shonk added that while the lightning strike rate during a winter thunderstorm is much lower than during summer storms, they can also be more damaging.

But both Weiss and Shonk said the biggest risk from the thunderstorms is the accompanying heavy snowfall. “Thundersnow usually only occurs during the most intense snowfall,” Weiss said, which can lead to poor visibility and dangerous travel conditions.

As of Monday (Jan. 6), winter storm warnings were still in place across the Central Plains to the Mid-Atlantic, with disruptive storm conditions expected to last through Monday night, the NWS said. States of emergency have been declared in Arkansas, Kansas, New Jersey, Missouri, Kentucky, Virginia and West Virginia, and 18 inches of snow fell in parts of Kansas overnight. The NWS also predicts up to 12 inches (30 centimeters) of snow Monday night across the Mid-Atlantic, including Washington, DC