(CNN) -- The warnings couldn't have been more dire. "DO NOT TRAVEL," the National Weather Service in Amarillo, Texas, posted on its website, telling residents not to venture out in what it was calling "a crippling, historic blizzard."
The storm was dumping snow over the Texas Panhandle at a rate of 2 to 3 inches an hour. Oklahoma also was being hit hard, and parts of Kansas and Missouri were under winter storm warnings.
In Woodward, a town in northwest Oklahoma, fire fighters were unable to reach a burning house because they ran into 4-foot snow drifts. The snow plow sent to dig them out also became stuck, Matt Lehenbauer, the director of Woodward, said Monday afternoon.
"At this point we can't keep ahead of snowfall rates," he said. "Right now the situation is pretty critical."
At least six calls came in from other stranded motorists, he said.
As of 3:30 p.m. (4:30 p.m. ET), 15 inches of snow had fallen in Woodward, the National Weather Service said.
Almost all roads in the Texas Panhandle were impassable, and whiteout conditions forced the state Department of Transportation to pull virtually all of its snowplows off roads, Texas DOT spokesman Paul Braun said Monday morning.
On its Facebook page, the weather service posted a video of the wind and snow whipping a U.S. flag outside its Amarillo office.
"If after watching the last video you thought you could still get out and travel, well you haven't seen anything yet!" the Facebook post said.
And later, it followed that up with another indication of how bad things were getting.
"Amarillo Airport just recorded a gust of 65knots/75mph! This is truly a historic blizzard!" the second Facebook post said. "Conditions have NOT improved. Please stay inside and do NOT venture out."
As of 4 p.m. (5 p.m. ET), 19 inches of snow had fallen in Amarillo -- an all-time single day record for February, the weather service said. Monday's accumulation also ranked as the second highest single-day snowfall accumulation ever recorded there, the agency said.
For some, the service's warnings didn't come soon enough.
Emergency crews were having trouble reaching drivers who were caught on the roads, Texas Department of Public Safety Trooper Gabriel Medrano said. Cars were in ditches, he said, because drivers couldn't tell where road ended and ditch began.
National Guard units were being sent to help stranded motorists, the Texas DOT said.
CNN iReporter Jason Boyett in Amarillo posted a video showing near-whiteout conditions at 7:40 a.m., and followed that with another showing a drift nearly 3 feet high outside his front door.
"We get high winds and we get big snowstorms, but they're not often combined," Boyett said.
Elsewhere in Amarillo, iReporter Michael Jaison shot video of the windblown snow outside his house. Drifts up to 3 feet high were forming, he said.
"I feel that we will be homebound for several days. There's no signs of the storm slowing down," Jaison said.
Whiteouts were also reported in Oklahoma, where as of 10 a.m. Central time, the state had closed all highways in six counties -- Ellis, Harper, Woodward, Beaver, Texas and Cimarron -- until further notice.
"Roadways and ditches are snow packed with no visibility and are very slick and hazardous. All travel is discouraged," the Oklahoma Department of Transportation said. As much as 16 inches of snow could fall in western areas of the state, the weather service said.
Oklahoma Lt. Governor Todd Lamb declared a state of emergency for 56 of Oklahoma's 77 counties.
Visibility was low in Fairview, Oklahoma, midway between the Panhandle and Oklahoma City, said CNN iReporter Brandi Whitacre.
"Right now it is snowing so heavily I can barely see down our driveway, which is 100 yards or so. It is coming down," said Whitacre, who added that'd she'd lost satellite TV service and was experiencing intermittent power outages.
The blizzard is the second major winter storm to hammer the region in a week.
The number of people under blizzard and winter storm warnings, watches and advisories totaled 35 million, according to CNN's weather unit.
"The unprecedented nature of this much snow in this short a period of time will create conditions ... across the entire city that are basically unprecedented for the traveling public," Joe Pajor of the Wichita, Kansas, Public Works and Utilities department, told CNN affiliate KSN. Parts of the area could see up to 26 inches of snow from the storm, the station reported, and the weather service said Wichita would be under a blizzard warning until 6 a.m. Tuesday.
Wichita schools were closed for the third straight school day as the new storm roared in on the heels of one that dumped up to 22 inches of snow on some areas late last week.
Kansas' governor on Sunday extended a state of emergency declaration to include the new storm.
"This storm has the potential to be more dangerous than last week's storm," Gov. Sam Brownback said. "So, we ask you to stay off the road unless it's absolutely critical. If you have to be out, be prepared with a charged cell phone, an emergency kit with food, water, blankets, flares and a shovel."
Brownback said Monday that one person had been killed in a single car accident in Sherman County. Officials blamed the fatal wreck on icy roads.
The Kansas Department of Transportation reported that many highways in the central part of the state, including Interstate 70, were completely covered by snow and ice on Monday morning.
With two storms dumping massive amounts of snow in quick succession, the weather service warned that structures may not be able to withstand the weight.
Schools closures were also reported from Colorado to Texas, as were the closing of many state and local offices.
All flights in and out of Rick Husband Amarillo International Airport in Texas were canceled until noon on Monday.
"Nothing coming in or out until then at the earliest," airport spokesman Daryl Ware said.
Preston Smith International Airport in Lubbock was also closed, CNN affiliate KCBD reported, and Texas Tech University in Lubbock shut down on Monday because of the storm.
And major highways in Texas, including portions of Interstate 40 and U.S. Highways 60, 87 and 187, were closed because of blizzard conditions.
"May see 4-6 foot drifts!" wrote National Weather Service meteorologist Rick Smith on Twitter. "Traveling is beyond discouraged!"
In Norman, Oklahoma, the University of Oklahoma closed Monday.
In Wichita, Pajor said the city used half of its road-clearing salt and sand in last week's storm.
To the east, Kansas City is expecting 9 to 15 inches of snow Monday night into Tuesday, according to the National Weather Service, and officials are telling residents to stay off the roads.
To the west, more than 9 inches of snow was reported in some areas of Denver by early Monday. Airlines in the Colorado capital were working to return to normal operations a day after more than 200 of 1,500 flights had been canceled and hundreds more flights were delayed because of the weather, according to the Federal Aviation Administration.
Up to 19 inches of snow was reported in Jefferson, about 70 miles southwest of Denver.
Forecasts of similar conditions raised alarms throughout the Plains, leading to crowded stores as residents prepared.
Amanda Roberts, an entrepreneur and blogger in Warrensburg, Missouri, where snow is expected to begin Monday night, went to the stores ahead of the storm.
"The snow has everyone stocking up on groceries," she said in a Twitter post. "Fresh produce is basically gone, but I got the last gallon of chocolate milk. I call it a win."
Rain, flooding the issue in Southeast
While millions will see snow -- including Chicago, where 3 to 5 inches of snow and sleet are expected Tuesday -- rain may rule for the next few days in parts of the Southeast.
In Mobile, Alabama, on the Gulf Coast, residents prepared for the possibility of heavy rain and wind gusts as strong as 30 mph by Monday night.
The rain is part of a band affecting five Southeastern states where flash flood watches are in effect from Monday afternoon through Tuesday morning.
Some areas from Louisiana to South Carolina could see up to 4 inches of rain.