Historic snowstorm hitting the South from Texas to Florida

Over 10 inches of snow has been reported in Louisiana as a historic, unprecedented snowstorm slams the South.

The snow is falling across Texas, Louisiana, Mississippi, Alabama, Georgia, South Carolina and Florida, bringing many roads to a standstill.

Authorities in Zavala County, Texas, said several people were killed in a major accident on slippery roads.

The Louisiana State Police said it has responded to more than 50 crashes on Tuesday and is urging everyone to stay home. The Lake Pontchartrain Causeway Bridge, which spans Lake Pontchartrain outside of New Orleans, has been closed.

In three Alabama counties, officials warned that all roads are impassible.

Over 2,100 flights are canceled across the United States. Houston's airports are closed and the Tallahassee International Airport is canceling all flights starting Tuesday afternoon. Houston's George Bush Intercontinental Airport and William P. Hobby Airport are expected to reopen late Wednesday morning.

Port Houston said all of its facilities will be closed Tuesday and Wednesday.

The wind chill -- what temperature it feels like -- has plunged to the single digits.

In Austin, Texas, county officials said they've responded to more than a dozen cold exposure calls, "including two fatal incidents." One hypothermia-related death was also reported in Georgia, according to James Stallings, the director of the Georgia Emergency Management and Homeland Security Agency.

The first-ever blizzard warning was issued for parts of Texas and Louisiana Tuesday morning.

Blizzard-like whiteout conditions were even reported around New Orleans, where residents are experiencing their biggest snowfall since 1963.

Most airlines at the Louis Armstrong New Orleans International Airport have canceled flights.

Schools are closed from Houston to New Orleans to Savannah, Georgia.

"Our reality is this, we can do hurricanes and tropical storms, alright? We don't do cold and we don't do ice well," Savannah Mayor Van Johnson said Monday. "If you don't have to go outside, don't. Stay home."

Louisiana's state offices will be closed Wednesday and Thursday, Gov. Jeff Landry announced during a press briefing Tuesday, noting "that tells you about how severe this weather event is."

"It's going to get dangerously cold over the next seven days," Landry warned. "Even if the roads start to look clear, please stay off them. Black ice is a big problem -- you can't see it, but it's extremely slippery and dangerous."

By Tuesday evening, the snow will be ending from New Orleans to Mobile, Alabama, to Atlanta, but it'll be ongoing across the Florida Panhandle, Georgia and the Carolinas. The snow will end overnight but very icy conditions will spread across Florida, causing an extremely slick morning commute.

ABC News' Alex Faul and Jason Volack contributed to this report.