A winter storm packing a frosty mix of snow and ice bore down on the US Northeast early on Saturday, disrupting post-holiday weekend airline traffic and prompting officials in New York and New Jersey to issue weather emergency declarations.

The National Weather Service posted ice storm and winter storm warnings throughout New York state and Connecticut, forecasting some of the heaviest snowfall totals — up to a foot in localised areas – for Long Island and the Hudson Valley.

New York City could see its highest accumulations since 2022, with peak snowfall rates of 2 or more inches per hour, according to an emergency declaration on Friday from Governor Kathy Hochul, warning of treacherous road conditions.

In many areas, snow was forecast to be mixed or glazed over with sleet and freezing rain.

“The safety of New Yorkers is my top priority, and I continue to urge extreme caution throughout the duration of this storm,” Hochul said in a statement, admonishing residents to “avoid unnecessary travel.”

Ice storm warnings and winter weather advisories were likewise posted for most of Pennsylvania, much of Massachusetts, and most of New Jersey, where a state of emergency also was declared.

High winds were forecast as part of the storm.

Snow began falling in western New York state and the New York City area on Friday evening and was expected to intensify on Saturday.

More than 1,600 commercial airline flights within the United States and into or out of the country were cancelled on Friday, and 7,800-plus were delayed as weather conditions began to worsen, according to the flight-tracking service FlightAware.

The three major airports serving the New York City area — John F. Kennedy, Newark Liberty International and LaGuardia Airport — accounted for the bulk of Friday’s flight cancellations.

All three issued alerts on the social media platform X, warning travellers of potential disruptions.

Another 650 flights that had been scheduled to depart or land in the US on Saturday were cancelled, FlightAware reported.

Representatives from American Airlines, United Airlines and JetBlue Airways told Reuters those carriers had waived change fees normally charged to re-book for passengers whose travel plans may be affected by weather-related disruptions.

New Jersey and Pennsylvania issued commercial vehicle restrictions for some roads, including many interstate highways.

“This storm will cause dangerous road conditions and impact holiday travel,” New Jersey’s acting governor, Tahesha Way, said in a statement.

“We are urging travellers to avoid travel during the storm and allow crews to tend to roads.”