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(CNN) -- Oh, weather, how moody you are!
The temperature ups and downs are downright extreme in parts of Texas. In less than 24 hours, Dallas went from a high of 81 degrees Fahrenheit at Love Field to a low of 17 degrees Monday morning, CNN meteorologist Sean Morris reported.
What's responsible for the sudden drop? A cold mass from Canada brought frigid air moving southeast across Texas, CNN meteorologist Todd Borek reported.
Across the Southern Plains, temperatures Monday afternoon were 30 to 40 degrees below normal, Morris said.
Sorry, fans of springtime: Temperatures are expected to remain below normal this week. Several more pushes of cold, arctic air will invade the United States east of the Rocky Mountains, Morris said.
As of now, it seems the snowstorms won't be record-setting, but several weak systems will cause some travel headaches, Morris said.
Washington, Baltimore and Philadelphia all got hit by snow Monday, and the Midwest and Great Plains were put into the freezer.
More than 2,950 U.S. flights had been canceled by Monday night, according to FlightAware.com, a flight tracking service. Ronald Reagan Washington National Airport had canceled about 80% of its departing flights by Monday afternoon, and Philadelphia International Airport had nixed about a third of its schedule.
People were feeling pretty fed up on Monday amid the third major storm of winter.
"I can't believe it's March and it's still snowing," Betsy St. John, from Brunswick, Maryland, told CNN affiliate WHAG. "I'm ready for spring."
This is a transitional season, and the most difficult time of year for meteorologists to put out an accurate forecast, Morris said.
The federal government closed offices Monday in Washington, which expects rain, ice and 4 to 8 inches of snow. Congress postponed Monday business until Tuesday. The Supreme Court was in session, however, hearing oral arguments and conducting other business.
Public school systems from Dallas to Philadelphia canceled Monday classes. Delaware, Tennessee and other states declared states of emergency. Amtrak cut service around Wilmington, Delaware, CNN affiliate WJLA reported.
There have been four weather-related auto fatalities. In Arkansas, a man was killed when he lost control of his SUV on Sunday in snowy weather and struck a retaining wall, the Arkansas State Police reported. In Oklahoma, a pedestrian was killed Saturday during freezing rain, the state's highway patrol reported.
And in Macon County, Tennessee, two people died in a two-vehicle crash as it began to sleet Sunday night, according to preliminary information from Dayla Qualls with the Tennessee Highway Patrol.
Virginia Gov. Terry McAuliffe declared a state of emergency there because of the storm -- a move that will help state agencies position resources where they're needed, McAuliffe said. The capital, Richmond, is expected to get 4 to 8 inches of snow and sleet, according to the National Weather Service.
McAuliffe said people in Virginia should postpone travel.
Schools in parts of North Carolina are closed as the storm is expected to bring sleet and possibly snow later Monday, according to CNN affiliate WRAL.
This storm is a national event that started out dumping rain on California, causing dangerous mudslides. It then moved east and delivered dangerous weather to places unfazed by typical winters.
Extremely low temperatures hit the Northern Plains, Upper Midwest and Great Lakes again. Highs from the single digits to the low 20s are expected from Montana eastward to New England, and subzero lows are likely for the Dakotas and the Upper Midwest.
Snow fell Sunday on Indianapolis, Louisville and St. Louis, where the weather caused numerous wrecks. Interstate 95 in northern Kentucky was shut down for a period Sunday.
In Little Rock, Arkansas, thousands of people woke up without electricity.
"We've got about 2,600 workers on the ground ready to go just as soon as the trouble begins," David Lewis, a spokesman with Entergy Arkansas, told CNN affiliate KATV. "With the forecasts being as firm as they've been, we have every reason to believe this will be a significant and serious winter storm."
Power outages were reported in Arkansas (14,000); Memphis (20,000) and Nashville (9,500) in Tennessee; Missouri (360); Mississippi (1,500); and Louisville, Kentucky (309).
The South will be cool but won't see much snow. There will be a slight risk of severe thunderstorms bearing damaging winds, a few isolated tornadoes and possibly large hail. People in Atlanta will feel temperatures in the 50s -- a big drop from Sunday's high of around 70.
The string of winter storms left many jurisdictions around the country low on road-clearing supplies.
In New Albany, Indiana, where salt is now in short supply, the city has shifted to a product called IMIX, which combines natural sand and calcium chloride, CNN affiliate WAVE reported.
In Virginia, the state Department of Transportation has already exceeded its $10 million snow removal budget by $3.4 million, CNN affiliate WRIC reported Sunday. Rhode Island got a new shipment of salt right before the storm, reported WPRI, a CNN affiliate.
Folks like Mariedith Poquiz of Frederick, Maryland, can't wait for the weather to warm up.
"I'm ready to break out my spring clothes," she told WHAG. "I'm tired of the winter."
CNN's Joe Sutton, Kevin Conlon and Katia Hetter contributed to this report.