Extreme weather across the US is snarling operations for companies including Walmart, GM, and FedEx

• Winter Storm Uri has snarled business for grocery stores, airlines, and mail carriers across the US.
• Walmart said it closed more than 500 stores, while Texas-based grocery chain H-E-B modified hours.
• USPS, FedEx, and UPS all announced service disruptions to their websites.

Extreme weather conditions this week caused businesses to shutter across the country.

Cold weather blasts in the Northeast, Midwest, South, which meteorologists have dubbed Winter Storm Uri and Winter Storm Viola, have caused a major power-grid manager to order rolling blackouts in 14 states Monday. Texas and surrounding areas in the South - which rarely experiences such cold winter weather - bore the brunt of outages as nearly 3 million people were without power due to record low temperatures.

Retailers, logistics firms, health clinics, and automakers shut down locations because of outages and other extreme weather risks.

Walmart said it closed more than 500 locations due to Winter Storm Uri. Most store closures impacted states in the South like Texas and Louisiana, according to an updated map.

"Due to winter storms in many areas of the US, we're closing some locations for the safety of our associates and customers," Walmart said in a tweet on Monday.

Other grocery stores reported closing locations:

• H-E-B modified hours of operation in locations across Texas.
• Kroger either closed or limited hours in stores around Dallas and Houston.
• Publix modified hours in 93 store locations around Birmingham and Nashville as of Tuesday afternoon.

The closings caused lines to form outside open grocery stores as residents stock up while they wait out the extreme weather. Snow, chilly winds, and freezing rain are expected to persist through midweek in the Great Plains and Mississippi Valley, according to NBC.

Extreme weather hit travel and logistics firms in the South

Businesses in the transportation and delivery sectors modified operations to keep customers and employees safe during the winter storm.

USPS, FedEx, and UPS all announced service disruptions to their websites. USPS, for instance, temporarily closed operations in parts of Alabama, Texas, Georgia, and Mississippi, while FedEx suspended Express service in parts of Alabama, Arkansas, Georgia, Kentucky, and Louisiana.

"Significant weather events across the US are impacting the UPS Network," the company announced on Tuesday. "Although your location may not be impacted by weather, the movement of packages in the network may be impacted by weather conditions in other areas."

GM, meanwhile, told Insider certain plants in Texas, Tennessee, Indiana, and Kentucky temporarily halted production due to "significant winter weather." Ford told The Detroit News they closed plants in Missouri.

A Nissan spokesperson told The Detroit Free Press the automaker temporarily suspended production at certain Tennessee and Mississippi plants, while Toyota told the paper it opted to shut down production in Texas, Kentucky, Indiana, and West Virginia.

Air transportation came to a halt in some areas after American, Southwest, and other airlines cancelled 800 flights Tuesday at Dallas Fort Worth Airport, The Dallas News reported.

American Airlines announced travel alerts in dozens of other locations, including Washington, Cleveland, and Albany, due to storms Viola and Uri.

Several states halted COVID-19 clinics and vaccinations due to the storms

Vaccination sites across Texas, Missouri, Alabama, and Michigan closed due to inclement weather.

Ascension Providence in Waco, Texas, announced the health system would close vaccine clinics through Wednesday, KWTX reported, and Dallas-based Baylor Scott & White closed all drive-through COVID-19 testing sites.

In West Virginia, the Cabell-Huntington Health Department closed its main building and postponed vaccine services due to inclement weather, per its website.

Nearly 40 million people in the US have received at least one dose of a coronavirus vaccine, according to the Centers for Disease Control and Prevention.