Ice may be more hazardous than snow this weekend. What to expect and how to prepare.

Winter storms and frigid temperatures are set to blast large swaths of the United States starting Friday, with more than 200 million people in the path of hazardous conditions, including sleet, ice, snow or extreme cold. The National Weather Service warned “nearly everyone east of the Rockies will see impacts.”

Among the most concerning aspects of the storm, forecasters say, is the havoc that could come from freezing rain and ice.

The weather service is forecasting “crippling ice and sleet” in the Southern Plains and Lower Mississippi Valley, and “the potential for long-duration power outages, extensive tree damage, and extremely dangerous or impassable travel conditions.”

“With sleet and snow, the effects are still very significant, but not to the same level as what the freezing rain can do,” said Corey Chaskelson, a senior weather service forecaster in Memphis, where 1-3 inches of snow and sleet and a half to one inch of ice is expected.

“It does not take much freezing rain to accumulate and make roads and any elevated surfaces, such as overpasses, very treacherous,” Chaskelson said.

Freezing rain occurs when snowflakes melt as they fall and refreeze, creating a glaze of ice on the ground, trees and power lines, or other objects.

A study frequently cited by state and federal environmental agencies found that accumulations of ice can increase the branch weight of trees by a factor of 10 to 100 times. A half-inch of ice can add 500 pounds of extra weight to power lines, according to the Air Force Safety Center.

“[Ice] is one of the primary causes of tree damage and power outages,” said West Virginia NWS meteorologist Simone Lewis. “It sticks more, it coats it and starts to weigh them down. It can really cause those power lines to sag and droop. It causes stress on the branches of trees and can cause large limbs to fall down.”

While snow can be plowed, ice is far more challenging to remove. Black ice, a thin, nearly invisible coating of ice that forms on surfaces like roads, sidewalks and driveways is a particular concern.

“I would tell you that I would rather have a snow storm than an ice storm,” Louisiana Gov. Jeff Landry said at a news conference Thursday, urging people to stay off the roads.

Preparing appropriately for ice is similar to preparing for heavy snow, but experts say that extra caution is needed when moving around outdoors in ice. Experts urge following weather service updates. (Check out NPR’s guide to what the different winter advisory levels mean).

The American Red Cross recommends creating a “Go-Kit” with at least three days of supplies and a “Stay-at-Home Kit” with at least two weeks of supplies.

While experts recommend avoiding travel and being outdoors in the storm, if travel is necessary, the National Weather Service recommends stocking your car with emergency supply kit items and filling up your gas tank ahead of time to keep your car’s fuel line from freezing.

Also, check your tires before leaving, as tire inflation drops in cold weather. Drive slowly and increase your following distance enough so that you’ll have plenty of time to stop for vehicles ahead.

“If you haven’t started your preparations for this storm, you should definitely be starting to do so now,” Lewis said. “We are expecting very hazardous travel conditions and widespread power outages, so it’s best to avoid travel and to prepare.”