Winter Storm Blair is impacting much of the U.S., bringing heavy snow, ice and frigid temperatures to the Mid-Atlantic states on Monday.

What To Know: Approximately 34 million people are under winter storm warnings and at least four deaths have been reported as the storm barrels across the country, according to the Weather Channel. Many school districts have closed and at least 18 inches of snow have fallen in some locations.

Affected Businesses: More than 350,000 people are without power due to the storm. Dominion Energy, Inc. (D  ), serves customers in Virginia where more 100,000 power outages have been reported.

Shares of portable-generator maker Generac Holdings Inc. (GNRC  ) have gained nearly 3% in the past five days as investors anticipated the storm-related power outages and increased demand for generators.

FlightAware is reporting nearly 3,000 flight delays and more than 1,700 cancellations as the storm moves across the country Monday. Southwest Airlines Co. (LUV  ) is reporting the most cancellations with 371, followed by American Airlines Group, Inc. (AAL  ) with 185 cancelled flights.

T-Mobile US, Inc. (TMUS  ) said it took proactive measures late last week, including fortifying network equipment, inspecting and fueling permanent and portable generators and reinforcing infrastructure, to ensure customers and first responders are able to stay connected throughout the storm.

What's Next: The wintry precipitation should wind down by Tuesday, but the Weather Channel expects another winter storm later this week.

"The next winter storm will begin to emerge in the Southern Plains by Wednesday night and especially Thursday. It could spread snow from parts of northern Texas, Oklahoma and Arkansas to other portions of the South, the Ohio Valley and possibly parts of the East by Friday or Saturday," weather.com Digital Meteorologist Chris Dolce said.