Temperatures to fall 10-25 degrees below average

A cold system will drop temps dramatically from the Tennessee Valley to the Northeast

With much of the country already cold, half the nation will be 10-25 degrees lower than average

Airlines are canceling flights ahead of time -- over 1,600 nationwide early Tuesday

Small but intense snow storm to dump up to 10 inches of snow in the Chicago area

(CNN) -- Kerplunk!

That's the sound of the temperature dropping early this week as a batch of cold air moves from the Tennessee Valley and lower Midwest over to the East Coast.

There will be 3 - 9 inches of new snow to go along with that from the Virginias to Massachusetts, the National Weather Service said. Much of it is expected to fall during daylight hours on Tuesday.

Add to that areas that are frigid already, and about half to the nation -- the eastern half -- will shiver through temperatures 10-25 degrees below average.

Snow and ice blanket downtown St. Louis and the Mississippi River on Wednesday, January 8.

People wait outside the Broadway Theatre in New York City to buy tickets for the show "Cinderella" on January 8.

Water dripping from a New York City subway station freezes on a traffic cone January 8.

A man walks past a car in Baltimore that is partially covered in ice January 8.

Ice collects on the Delaware River near Philadelphia on January 8.

Icicles hang from the bumper of a vehicle in Fort Walton Beach, Florida, on Tuesday, January 7.

A vehicle drives through a barely visible intersection in Stafford, New York, on January 7.

Plants covered in ice are seen in Panama City Beach, Florida, on January 7.

Ice in the Mississippi River flows past the Gateway Arch in St. Louis on January 7.

Ice forms around rocks on the Brooklyn waterfront, across from Lower Manhattan, on January 7, in New York City.

A woman braves the cold in Scranton, Pennsylvania, on January 7.

Passengers wait for a train to arrive in Chicago on January 7, when temperatures were below zero.

A man clenches his fists while walking past a steam vent in New York City on January 7.

A man bundles up against the cold in New York City on January 7.

A couple walks past an advertisement in Pittsburgh during sub-zero temperatures January 7.

A woman tries to stay warm while waiting for a bus in Brooklyn, New York, on January 7.

Ice builds up along Lake Michigan at Chicago's North Avenue Beach on Monday, January 6.

With temperatures nearing 0 degrees, a cloud of steam from a manhole blows across an intersection in downtown Pittsburgh on January 6.

Men battle the bitter wind as they walk in Chicago on January 6.

Postal worker Jamie Jasmon struggles to deliver mail in the snow January 6 in Springfield, Illinois.

Vehicles drive down a snow-covered road in Burton, Michigan, on January 6.

Metra employees in Chicago walk around LaSalle Street Station on January 6.

A man warms his hand while running errands in Flint, Michigan, on January 6.

A commuter walks past warming lamps at a Chicago train station on January 6.

A woman props up her feet on her luggage January 6 after her flight home was canceled at Logan International Airport in Boston.

A woman makes her way through a snow drift in downtown St. Louis on January 6.

A man shovels the snow off his car in Indianapolis on January 6.

A woman walks to the University of Minnesota's St. Paul campus on January 6.

A man clears the sidewalk in front of his home in Carmel, Indiana, on January 6.

A blanket of fog covers Lake Michigan along the Chicago shoreline January 6.

A man braves the snow in downtown Springfield as a winter storm moves across the Midwest on Sunday, January 5.

A car is buried in snow January 5 in Zionsville, Indiana.

A city snowplow clears the street in an almost-deserted downtown Springfield on January 5.

With the Gateway Arch in the distance, a person struggles to cross the street during a snowstorm January 5 in downtown St. Louis.

Snow covers a garden gnome in St. Louis on January 5.

Anna Maksimkina of Yekaterinburg, Russia, sleeps on the floor at John F. Kennedy International Airport in New York after a Delta flight from Toronto to New York skidded off the runway into a snow bank, temporarily halting all flights January 5.

Four homeless men warm themselves on a steam grate by the Federal Trade Commission Building, blocks from the U.S. Capitol in Washington, as frigid temperatures grip the nation's capital on Saturday, January 4.

People go sledding in Prospect Park in Brooklyn, New York, on January 4.

Snow is piled high in front of a Home Depot in Boston on January 4.

Sunlight beams through the windows of a building that caught on fire Friday, January 3, in Plattsmouth, Nebraska. The firefighters' water froze all over the building.

Michael Stanton walks between houses covered with ice in Scituate, Massachusetts, on January 3.

Pedestrians brave wind and snow as they cross New York City's Fifth Avenue on January 3.

Snow clings to the clothing and facial hair of Jerome Williams as he uses a snowblower in front of his home in Roosevelt, New York, on January 3.

Travelers wait in line January 3 at Chicago Midway International Airport.

Frost covers the windows at the Morning Glory natural food store in Brunswick, Maine, on January 3.

Snowplows clear snow from one of the runways at JFK Airport on January 3.

Surfers make their way through snow on New York's Rockaway Beach on January 3.

Passengers wait in line at a security checkpoint at JFK Airport on January 3.

Blowing snow swirls as a worker shovels a platform at a Haddonfield, New Jersey, train station on January 3.

A plane takes off January 3 as trucks plow snow at Newark Liberty International Airport in Newark, New Jersey.

A man walks down a snowy road along the shore in Scituate on January 3.

Postal worker Danny Kim clears snow and ice off the hood of his delivery truck January 3 in Bethesda, Maryland.

A couple walks across a snow-covered parking lot January 3 at Newark Liberty International Airport.

Tourists play in the snow at the base of the Washington Monument on January 3.

People play in Brooklyn's Prospect Park on January 3.

A man walks through the snow as the wind kicks it up January 3 in New York City.

Dante de Blasio, son of New York Mayor Bill de Blasio, shovels snow outside his home in Brooklyn on January 3.

Snow covers subway rails in New York City on January 3.

A man uses his snowblower to clear some paths in Mansfield, Connecticut, on January 3.

Workers clear snow off sidewalks on New York City's Fifth Avenue on January 3.

A man clears snow from a vehicle January 3 in Albany, New York.

A truck-mounted snowblower clears a section of road in Dedham, Massachusetts, on January 3.

A worker clears snow from a subway station in Queens, New York, on January 3. Public schools were closed Friday after up to 7 inches of snow fell in New York City.

A man shovels snow during the tail end of a snowstorm in Brooklyn on January 3.

A man rides an all-terrain vehicle through a Brooklyn street on January 3.

The Kunta Kinte-Alex Haley Memorial is covered in snow in Annapolis, Maryland, on January 3.

A man plows snow January 3 following an overnight snowstorm in Jersey City, New Jersey.

A child sleds down a hill in Chicago's Humboldt Park on Thursday, January 2.

Children make a snow pile in New York's Times Square on January 2.

Winds whip snow from the beach across Winthrop Shore Drive in Winthrop, Massachusetts.

Snow covers bikes along Leavitt Street in Chicago's Wicker Park on January 2.

With his dog in tow, a man skis across heavy snow in Humboldt Park on January 2.

Dallas Todd, 11, flies down a snowy hill at Lake Harbor Park in Norton Shores, Michigan, on January 2.

Snow covers cars in Chicago's Humboldt Park neighborhood on January 2.

A man drags a suitcase on a snowy street in downtown Boston on January 2.

A van is pulled from a ditch along Interstate 94 in Jackson, Michigan, on January 2.

A man walks his dog on the snow-covered Monon Trail in Carmel, Indiana, on January 2.

An airplane waits for passengers at O'Hare International Airport in Chicago on January 2.

A woman walks through snowy conditions in Albany on January 2.

Trucks clear snow off the roads in Torrington, Connecticut, on January 2.

Winter weather grips U.S.

Photos: Winter weather grips U.S.

A Chicago resident's eyelashes froze on the morning of January 6.

CNN iReporter Robert Livesay took this picture of frozen ice bubble he blew in Grove, Oklahoma, on Monday, January 6. "If you have too much wind, the bubbles will blow away," he said.

A little snow won't stop these two from enjoying a run in northeast Ohio on January 6.

A Chicago man heads to work on January 6 with an overcoat and briefcase ... plus a balaclava and ski goggles.

Maranda McClaskey knew the birds in Harrisville, West Virginia, would appreciate extra food in the chilly weather on January 6. But when one poor bird landed on her porch to eat, it got stuck to the ice! Finally the bird managed to free itself -- but it left these feathers behind.

Sixteen-year-old student Christian Arnold photographed a snowdrift in Indiana on January 6. "This is the most dangerous winter weather I have ever witnessed," he said.

In Wisconsin on January 6, temperatures fell to minus 21 degrees, with wind chills below 40.

Nature photographer Candice Trimble bundled up in layers to snap some shots of the frozen conditions outside her home in Front Royal, Virginia, on Sunday, January 5. She watched this water hit the leaf and then completely freeze.

Is this guy nuts?! He's sporting shorts in Chicago on January 6, when the temperature did not rise above 0 degrees Fahrenheit.

Trees are weighed down with snow in the Long Lake area in Michigan on January 5.

The frigid weather inspired photographer Tanya Fuchs to take her camera out around her neighborhood in Fire Island, New York, on Saturday, January 4.

CNN iReporter Joy Lewandowski's son Matt plays in a snow fort built by kids on her street on January 5. School was canceled Monday.

Jason Bentley decided to take a relaxing break in the snow on January 5 in Indianapolis, Indiana, after he learned that his Southwest flight back home to Los Angeles was canceled and rescheduled for Thursday.

CNN iReporter Todd Joyce took this photo of his dog, Ginger, playing in the snow in Ohio on January 5.

Alexandra Leahy ventured outside her apartment complex in Carmel, Indiana, on January 5 to photograph the snowy landscape. "The snow is very white, very glistening, and stuck to everything," she said.

Mark Anthony Baquir captured this photo of a snowy yard in Maryland on Friday, January 3. "It seemed like no one was prepared for the storm in this part of Maryland," he said.

Your winter weather photos

Passengers unload their luggage at Chicago's Union Station after their Amtrak train became stuck in snow drifts on Tuesday, January 7.

A man walks past a snow-covered bicycle in Chicago on January 7.

People ride a street car in New Orleans as temperatures in the area plummeted below freezing on January 7.

A passenger waits for a train to arrive in Chicago on January 7, when temperatures were below zero.

JetBlue passengers in Boston wait for normal flights to resume at Logan International Airport on January 7.

A man takes a nap at Logan International Airport after his flight was canceled Monday, January 6.

Commuters wait for a Virginia Railway Express train to arrive at Washington's L'Enfant Plaza on January 6.

A Delta Air Lines plane is de-iced at Chicago Midway International Airport on January 6.

A commuter walks past warming lamps at a Chicago train station on January 6.

A jet is de-iced at Gerald R. Ford International Airport in Grand Rapids, Michigan, on January 6.

A man and woman do their best to get comfortable while stranded at Lambert-St. Louis International Airport on Sunday, January 5.

Travelers get off a shuttle bus at Chicago O'Hare International Airport on January 5.

A passenger takes a nap inside Los Angeles International Airport on Friday, January 3, after his flight was canceled because of the weather on the East Coast.

An airplane is de-iced at Ronald Reagan Washington National Airport on January 3.

Snowplows clear snow from one of the runways January 3 at John F. Kennedy International Airport in New York City.

Travelers in Boston leave the Back Bay train station on January 3.

An airport employee clears snow at New York's LaGuardia Airport on January 3.

Travelers wait in line January 3 at Chicago Midway International Airport.

A plane takes off from Newark Liberty International Airport in Newark, New Jersey, as trucks plow snow on the tarmac January 3.

A woman sleeps on the floor of New York's JFK Airport on January 3.

Cars sit covered in snow at Chicago O'Hare International Airport on Thursday, January 2.

Icicles hang from a window looking onto airplanes at Logan International Airport in Boston on January 2.

Winter weather slows travel across U.S.

Photos: Winter weather slows travel across U.S.

Cold weather good for farmers

The vast area is expected to stay in the icebox until the weekend. That can mean lows in the teens in Memphis, Tennessee, and in the single digits from Louisville, Kentucky, to Boston.

A second frigid weather system is moving down from Canada, and will plunge low temperatures into the double-digit minus degrees all along the border. Whipping winds will knock the wind chill down to 20 - 40 below zero from the Upper Plains states to northern Missouri.

A small but intense snow storm is dumping up to 10 inches of snow in metropolitan Chicago as moisture over Lake Michigan mixes with frigid air.

Transportation woes

Though it covers only a small area, Chicago's storm appears to be enough to make air traffic at least more annoying. O'Hare International had cancelled about 5% of flights in and out of the airport before dawn on Tuesday, according flightaware.com.

But much more frightful aviation nightmares appear to be taking hold in the Northeast. From New York City to Washington, major airports had canceled a quarter to a third of scheduled flights by early Tuesday.

At Philadelphia's airport, Southwest Airlines plans to suspend operations at 3:00 p.m., when the flakes are expected to be falling at full tilt.

Even Boston's Logan airport had reduced air traffic by at least 20% early Tuesday, according to flightaware.com.

The cancellations at snow-doused airports may cause ripple effects throughout the nation's air traffic system.

About 1,700 flights had been canceled nationwide as of early Tuesday, flightaware reported.

Ohio, state of emergency

The icy weather has collided with a shortage of propane and heating oil in Ohio, CNN affiliate WKYC reported.

More than 10% of residents have tanks of one of these fuels attached to their homes to warm them against the brutal cold.

Joe Butano is one of them, and on Monday, with more cold on its way, his propane tank was less than half full.

Customers are clamoring for what is left, and Butano is afraid of coming up short. He has added portable electric heaters and firewood to the mix.

"It makes sense where there's a shortage, it just seems to make sense in preparation for what's the worst that could come," he told WKYC.

The shortage may seem like an inconvenience for customers like Butano, but Ohio's government is taking the shortage paired with the intense cold more seriously than that.

Gov. John Kasich has declared a state of emergency that allows trucks carrying hazardous materials -- like propane or heating oil -- to be on the road longer.

Fuel suppliers also warn that the dearth is acute. Propane company The Gas House hasn't seen one like this one in 23 years.

"I'm concerned because I don't know when we're getting it or if we're getting it, and all the propane companies are in the same boat," said spokesman Scott Zura.

Nice outside

Some sidewalk cafes got crowded in the nation's capital Monday, as people enjoyed that last temperate day before the cold snap's arrival, CNN affiliate WJLA reported.

"I'm loving this today; this is true winter weather for me," Bill Dilodovico said.

Some Washingtonians were soaking up the weather in shorts and T-shirts.

"It is fantastic yet ironic at the same time," said Dan Tarvin, who was out jogging ahead of the icy weather. Tuesday, he'll be running indoors.

Others opted to use the day to brace for what may come -- Larry Luebbers of Oakton, for example.

"I picked up my snowblower, I got gas ... four-wheel drive, so I'm ready to go," he told WJLA.

Pam Rao and her son Josh of Vienna, Virginia, were looking forward to the snow. "It's a lot of fun, and you know, you only get it once a year or twice a year in this area, so, it's good," said Pam.

Dozens of schools in and around the District of Colombia will shut their doors Tuesday, WJLA reported.

Josh hopes to get a one day off, at least.