Category 5 March Blizzard Shuts Mackinac Bridge, Paralyzes Upper Midwest and Sparks Tornadoes in South

Snowbanks rose higher than pickup trucks in Marquette, Michigan, on the morning of March 16. Plows carved narrow canyons through 3 to 4 feet of fresh snow. The Mackinac Bridge — the five-mile lifeline between Michigan’s Upper and Lower peninsulas — was closed to all traffic as wind-driven snow whipped across the Straits of Mackinac.

By the time the last bands of heavy snow pulled away from the Great Lakes, federal meteorologists had given the storm a rare distinction: a Category 5 rating on the National Oceanic and Atmospheric Administration’s Regional Snowfall Index (RSI), the highest level on a scale that measures the most disruptive winter storms in modern U.S. history.

It was the first time in a decade that a blizzard had reached Category 5, a label shared with the legendary storms of 1978, 1993 and 2016.

The mid-March system — unofficially dubbed Winter Storm Iona by a cable weather network — formed on March 13 and intensified as it moved from the Pacific Northwest to the northern Plains and Upper Midwest. It buried parts of Wisconsin and Michigan’s Upper Peninsula under more than four feet of snow, shut down interstates from the Dakotas to New England, knocked out power to more than half a million customers in the United States and tens of thousands in Canada, and spun off dozens of tornadoes and a wall of dust in the South.

The same week, much of the country lurched between weather extremes: polar-vortex cold in the Midwest and East, a heat dome in the Southwest, and an atmospheric river drenching Hawaii. It was a vivid snapshot of what one federal forecaster described as a jet stream “gone wild.”

“All of the country… are going to see generally changing from cold to warm, or warm to cold to warm,” said Marc Chenard, a meteorologist at the National Weather Service’s Weather Prediction Center, in an interview during the stormy week.

A blizzard from Seattle to Sudbury

The system’s evolution began on March 13, when an atmospheric river from the Pacific collided with Arctic air spilling south over the northern Rockies and High Plains.

In Washington state, Seattle-Tacoma International Airport logged three inches of snow and more than an inch of liquid precipitation, both daily records. Snoqualmie Pass reported roughly two feet of new snow, forcing closures on Interstate 90 after multiple crashes. Heavy, wet snow knocked out power to thousands in Idaho and Montana.

As the storm crossed the Rockies on March 14, it reorganized as a Colorado low — a familiar breeding ground for major Central U.S. winter storms. Emerging over the Plains, the low deepened rapidly under a powerful jet stream, setting the stage for a classic blizzard.

By late March 14 and early March 15, the Weather Prediction Center was warning of “major mid-March blizzard conditions” from eastern South Dakota through Minnesota, Wisconsin and northern Michigan. Forecasts called for snowfall rates of 1 to 3 inches per hour, totals up to 1 to 3 feet or more, and winds gusting to 60 mph.

Minnesota Gov. Tim Walz declared a peacetime emergency on March 13, activating the National Guard as forecasters warned of potentially crippling snow around Minneapolis and southern parts of the state. Wisconsin Gov. Tony Evers followed with a state of emergency on March 14 to mobilize resources for plowing and power restoration. In Michigan, Gov. Gretchen Whitmer activated the State Emergency Operations Center on March 15 and later declared an emergency for seven Upper Peninsula counties where snow totals would prove historic.

The core of the blizzard took shape on March 15 and 16 as the storm center reached the Upper Midwest. At 7 a.m. Eastern time March 16, surface analyses from the Weather Prediction Center placed the low at about 983 millibars over Michigan — a deep pressure reading for an inland system — with a broad shield of heavy snow wrapping around its northwest side.

In Wisconsin, Wausau set a daily snowfall record on March 15 with 23.4 inches and a three-day total of 30.2 inches, the most snow it had ever recorded over three consecutive days. Green Bay logged 26.6 inches from the storm, its second-highest total on record, with several nearby communities reporting 30 to 34 inches.

Across the border in Michigan’s Upper Peninsula, totals were higher still. Near the small community of Round Lake, unofficial reports put snowfall at about 52 to 54 inches. The National Weather Service office near Marquette measured 36.3 inches in just two days, breaking its previous two-day record by nearly five inches. Blizzard conditions and dangerous crosswinds forced the full closure of the Mackinac Bridge, briefly cutting off road access between Michigan’s peninsulas.

Farther east, a zone of freezing rain coated parts of northern Lower Michigan in up to three-quarters of an inch of ice, snapping tree limbs and power lines. At the height of the storm, about 140,000 customers in Michigan were without electricity.

The system did not stop at the Great Lakes. As it accelerated into Ontario and Quebec, heavy snow and high winds shut highways in northeastern Ontario and prompted the city of Sudbury to declare a “significant weather event.” Sudbury recorded more than 40 centimeters (about 16 inches) of snow, its heaviest one-day snowfall since 1959. Sault Ste. Marie tallied around 55 centimeters. Two sports domes in Sudbury collapsed under the weight of the snow, according to local officials.

South side: tornadoes, dust and dangerous winds

While the northern flank of the storm produced blizzard conditions, the southern and eastern sides generated a different set of hazards.

On March 15, the Storm Prediction Center issued an “enhanced” risk for severe thunderstorms from the lower Mississippi Valley into the Deep South and lower Ohio Valley. A powerful cold front and strong wind shear helped spawn 51 confirmed tornadoes, most rated EF0 or EF1, in states including Missouri, Arkansas, Tennessee, Kentucky, Alabama and Georgia. Damage surveys described uprooted trees, damaged roofs and barns, and mobile homes rolled or shifted off foundations. Straight-line wind gusts reached at least 77 mph in parts of Arkansas.

In North Texas, 60-mph winds associated with the same sprawling system toppled trees and power lines, closing stretches of Interstate 35E in Denton and triggering cancellations of outdoor events and theme park operations. Tens of thousands of customers lost power across North and East Texas.

Along the storm’s sharply defined cold front in West Texas, satellites captured a dramatic wall of dust racing south. Visibility on some highways briefly dropped to near zero, contributing to multi-vehicle pileups.

As the low re-intensified near the East Coast and Canadian Maritimes on March 16 and 17, a broad field of damaging winds swept through the Mid-Atlantic and New England. Gusts reached 72 mph at John F. Kennedy International Airport in New York, 74 mph on the barrier island of Avalon, New Jersey, and 81 mph at Massachusetts’ Blue Hill Observatory. Trees and limbs crashed onto homes, vehicles and power lines, leaving tens of thousands without electricity across Maryland, Delaware, New Jersey, New York, Connecticut, Rhode Island, Massachusetts and Vermont.

At least two people were killed in wind-related incidents in the Northeast, including a man struck by a falling tree in a Philadelphia suburb and a driver who crashed while swerving to avoid a downed tree in New York’s Westchester County, according to local authorities.

A Category 5 in context

NOAA’s Regional Snowfall Index classifies winter storms for six U.S. regions from Category 0, a “nuisance,” to Category 5, “extreme.” The index combines snowfall totals, the geographic area covered and the number of people impacted to produce a single score. Storms in the top category, with scores above 18, are rare.

The March 2026 blizzard received an RSI value of 26.97 for the Upper Midwest region, placing it firmly in Category 5 territory. It is the first RSI Category 5 storm since the January 2016 blizzard that buried parts of the Mid-Atlantic and Northeast and ranks among the most impactful March snowstorms in the modern record for the Upper Midwest.

Since 1900, only a few dozen storms have earned Category 5 status nationwide, including the Great Blizzard of 1978 and the March 1993 “Superstorm.”

“This is not your average March snow,” said one Weather Prediction Center forecaster in a public discussion ahead of the event, warning of “blizzard conditions and potentially record-breaking snowfall” from Minnesota to northern Michigan and urging residents to avoid all but essential travel.

Despite several days of advance warning, the Minnesota State Patrol reported 464 crashes between March 13 and 15, including 40 with injuries and one fatality. In Iowa, state troopers counted 99 crashes and 299 motorist assists between March 15 and 16, with one person killed. A driver in Nebraska’s Lancaster County died in a whiteout-related crash, according to local officials. Those preliminary tallies do not include tornado and wind casualties in the South and East.

By the morning of March 16, roughly 5,000 flights had been canceled across the United States, according to aviation tracking data, with major disruptions at hubs in Seattle, Minneapolis, Chicago, Detroit, Boston and New York.

Weather whiplash in a warming world

The March blizzard struck in a winter already marked by swings between extreme cold and unusual warmth. Just weeks earlier, a separate February storm brought deadly snow and wind to the Northeast and Mid-Atlantic. At the same time Iona was burying the Upper Midwest, Phoenix was under a heat dome and forecasting temperatures flirting with the season’s earliest triple-digit readings, and Washington, D.C., had toggled from record 80-degree warmth to snow in a matter of days.

Ryan Maue, a meteorologist and former chief scientist at NOAA, said the pattern meant “extreme weather in all 50 states,” tying together the blizzard, a Southwest heat wave, the Hawaii atmospheric river and outbreaks of severe thunderstorms.

Climate scientists caution against attributing any single storm exclusively to climate change. But decades of research show that a warmer atmosphere can hold more water vapor, which increases the potential for heavy precipitation — including heavy snow — when cold air is in place. Other studies have suggested that a warming Arctic and declining sea ice may sometimes be linked to a more contorted jet stream and displaced polar vortex, though that connection remains an area of active debate.

The March 2026 storm also unfolded against the backdrop of a strong El Niño, a natural climate pattern in the Pacific Ocean that tends to energize the subtropical jet stream and can favor stronger storms across the southern and central United States.

A preview of winters to come

For residents digging out in Green Bay, Marquette, Sudbury and dozens of smaller communities in between, those larger debates are now layered over lived experience.

In the Upper Peninsula, where snow is a fact of life, longtime residents told local media they had not seen drifts that high in years. In rural areas of the Dakotas and northern Wisconsin, “no travel” advisories and impassable roads isolated some communities for days. Linemen and utility crews worked around the clock across multiple states to restore power amid dangerous wind gusts.

As damage assessments continue, officials and researchers are beginning to treat the March 2026 blizzard as a case study in how a single, sprawling storm can stress transportation, power and emergency systems from one end of the continent to the other.

For meteorologists, the Category 5 designation secures the storm’s place in the record books. For those who spent days trapped at home, stranded on highways or working through the night to keep the lights on, it will linger as a memory — and a reminder that even in mid-March, winter in North America can still flip into extreme, and do it fast.