CAMBRIDGE, Mass. — A major winter storm was on a path Friday to wallop as many as 80 million people in the Midwest and Northeast over the weekend with a punishing mix of heavy snow, strong winds and frigid temperatures.

In Kansas, officials dispensed warnings to ranchers about how to keep their horses from freezing to death. Small towns notified residents that their plows might not keep up with the rapid snowfall, leaving streets impassable. And, in a foretaste of the chaos likely to ensnarl the country’s transportation networks, hundreds of flights were canceled at Chicago’s O’Hare International Airport, before a single snowflake had fallen there.

The storm was also expected to further strain the National Weather Service, where many employees have been furloughed as part of the partial government shutdown. Others — including those putting out the storm warnings that state and local officials rely on for their planning — are considered essential and are working without pay.

“I’ve been working for the National Weather Service for over 27 years — I’ve never seen the morale as low as it is right now,” said Dan Sobien, the president of the National Weather Service Employees Organization.