Almost 4,000 flights were canceled in the US on Saturday ahead of a monster winter storm that has already cut power to thousands of utility customers as far west as Texas, and threatened to paralyze eastern states with heavy snowfall.
Forecasters said snow, sleet, and freezing rain, accompanied by dangerously frigid temperatures, would sweep the eastern two-thirds of the nation on Sunday and into next week.
Calling the storms "historic," US President Donald Trump on Saturday approved federal emergency disaster declarations in South Carolina, Virginia, Tennessee, Georgia, North Carolina, Maryland, Arkansas, Kentucky, Louisiana, Mississippi, Indiana, and West Virginia.
"We will continue to monitor, and stay in touch with all States in the path of this storm. Stay Safe, and Stay Warm," Trump wrote in a post on Truth Social.
Several states and the District of Columbia have declared weather emergencies.
The US National Weather Service warned of an unusually expansive and long-duration winter storm that will bring widespread, heavy ice accumulation in the southeast US and cited "crippling to locally catastrophic impacts."
Weather service forecasters predicted record cold temperatures and dangerously cold wind chills descending further into the Great Plains region of the US by Monday.
As of 5 p.m., more than 3,900 US flights scheduled for Saturday had been canceled, according to flight tracking website FlightAware. More than 8,800 US flights originally set for Sunday also have been canceled, the website indicated.
Major US airlines warned passengers to stay alert for abrupt flight changes and cancellations.
In an update on its website on Saturday morning, Delta said it “continues to make schedule adjustments due to Winter Storm Fern,” with additional cancellations in the morning for Atlanta and along the East Coast, including Delta hubs in Boston and New York City.
The airline said it was relocating experts from cold-weather hubs to support de-icing and baggage teams at several southern airports.
US electric grid operators on Saturday stepped up precautions to avoid rotating blackouts.
Dominion Energy, whose Virginia operations include the largest collection of data centers in the world, said if its ice forecast holds, it could be among the largest ever winter events to affect the utility's operations.
Frigid weather stresses US electric grid
US electric grid operators on Saturday stepped up precautions to avoid rotating blackouts, as frigid weather hitting half of the country's population stressed their operations.
The PJM Interconnection - the largest US regional grid that serves 67 million people in the East and Mid-Atlantic - reported temporary spikes in spot wholesale electricity prices that soared above $3,000 per megawatt hour on Saturday morning from earlier levels of less than $200 per MWh.
PJM boosted its forecast for Tuesday, predicting an all-time high for winter electricity demand at 147.2 gigawatts. That would beat the current record of 143.7 GW set in January 2025.
Spot wholesale electricity prices across the US were volatile throughout Saturday, surging several times higher in New England and the Midwest, for example, than during normal winter operating conditions.
Spot prices on ISO New England, the grid for six states, surged to nearly $600 per MWh, up sharply from Friday when prices were below $100 MWh during parts of the day.
Meanwhile, older power plants, typically idled much of the year, came online to take advantage of the elevated prices to serve higher-than-expected demand, said Georg Rute, CEO of grid software company Gridraven, and an expert on how weather affects power line capacity.
"A 40-year-old gas turbine switches on because it sees these super-high prices," Rute told Reuters. He added it was a sign of stress in the PJM system and elsewhere.
Prices also soared in other regions as stormy weather and temperatures hovering around 0 degrees Fahrenheit (-18 Celsius) pushed up electricity demand and prompted some operators to shut in natural gas production in key basins, while grid companies also faced constraints on gas pipeline supply.
Dominion Energy, whose Virginia operations include the largest collection of data centers in the world, said if its ice forecast holds, it has the potential to be one of the largest winter events to affect the utility's operations.
While regional grid operators juggle restricted fuel supplies, congested transmission lines and wild weather, electric utilities are staging crews to repair expected ice and snow damage on low-voltage distribution lines that bring power to homes and businesses.
Grids face strain
Faced with constricted gas supplies, regional US grid operators are asking coal and gas-fired power plants to boost output, according to grid operations reports.
The Midcontinent Independent System Operator called on power plants to maximize output and curtailed electricity exports in a territory that stretches across 15 states in the Midwest and South and Manitoba, Canada.
Over the past 24 hours, MISO imported up to several thousand megawatts of power from PJM's territory to meet demand, according to MISO's operations reports.
PJM faces greater reliability threats in winter because natural gas plants - the backbone of its generation - frequently face fuel supply constraints and mechanical freezing during extreme cold, according to analysts at consulting firm ICF International.
Neighboring grid MISO issued an all-hands-on-deck emergency action designed to avoid capacity shortfalls as some power plants are forced offline or reduce their output because of freezing temperatures. This alerted utilities to be prepared to produce as much electricity as possible.
MISO spot wholesale electricity prices soared to above $400 per MWh throughout the grid operator's territory as the upper Midwest experienced transmission bottlenecks across high-voltage power lines. Electricity prices in MISO's southern territory, which were less than $50 per MWh earlier on Saturday, rose above $200 per MWh in parts of Louisiana and Mississippi, MISO reported.
In New England, fuel oil generation kicked into high gear to help the six-state region's electric grid conserve natural gas, its top fuel source.
As evening approached on Saturday, oil-fired generation accounted for 38% of the New England grid's output, compared with a typical level of about 1% or less, ISO New England's operations display showed. Natural gas, usually the grid's main fuel source, accounted for 24% of the grid's generation output.
Texas grid tested
For the Electric Reliability Council of Texas, the winter storm is the biggest test for the state's main grid operator since 2021, when a storm nearly caused a catastrophic regional blackout.
More than 200 people died as ERCOT lost about half of its generation capacity amid frigid weather.
Since then, stricter state and federal rules have been implemented to require better winter readiness by utilities and grid operators throughout the country.
Rute said ERCOT appears to be in good shape as it has abundant fossil-fuel generation, big contributions from wind and solar power, and more battery storage than any other grid.
"I think there's very little chance of a (2021) rerun," he said. "But no blackout happens the same way twice."
'Take the storm seriously,' National Weather Service warns
This follows a warning from the NWS on Friday that the storm would be set to affect 40 states throughout the weekend, including heavy snow, freezing rain, and sleet.
According to the data shared by the NWS, people in the North-East coast and the center of the country are expected to see heavy rains and snow in the coming days, with a warning of "considerable disruptions to daily life" issued by the authorities.
"Take this storm seriously, folks," said the NWS in a statement, and added, "Hazardous to impossible driving conditions are expected. Avoid travel if at all possible. Widespread closures and disruption to infrastructure may also occur."