April Sprinkle, 27, places a weed barrier over pansies at a Star Nursery on West Charleston. The barrier will protect the plants from the extreme cold weather coming to the valley this weekend. Photo by Clint Karlsen.

It's about to get cold. Really, really cold.

An arctic air mass from the north will move into Southern Nevada in the coming days, bringing bone-chilling temperatures and probably even a bit of snow.

"No records are going to be approached, but it's still going to be cold," said John Feerick, a forecaster for accuweather.com.

The cold air was expected to hit tonight and linger through the weekend. Highs will hover around 40 degrees, and overnight lows will plunge into the 20s, dropping to the low 20s on Saturday night.

The temperatures will be among the lowest since December 1990, when lows at McCarran International Airport hit 18 degrees.

Weekend lows could hit the teens under the right conditions, said Jim Harrison of the National Weather Service.

The cold weather is expected to bring snow on Friday. Forecasters predicted 1 to 3 inches falling across the valley.

"I wouldn't be surprised if we saw some snow showers, even on the Strip," Feerick said.

Despite the cold, no records will be threatened. The lowest temperature recorded on Jan. 13 was 8 degrees in 1963. That was the lowest temperature ever recorded in Las Vegas. The record low for Jan. 14 was 14 degrees that same year.

The freezing overnight temperatures could cause exposed water pipes to freeze and burst, and many plants and trees could be damaged or killed.

Officials recommended insulating exposed water pipes or leaving faucets dripping during the freeze. Plants and trees can be protected by wrapping them in burlap or other protective covering.

"We're crossing our fingers that the weatherman is wrong," said Yvette Monet, spokeswoman for MGM-Mirage, which has thousands of fragile palm trees on its properties.

The Mirage alone has about 4,000 palm trees.

During the cold snap in 1990, many of the palm trees at The Mirage died. Hotel workers painted the dead trees to make them look alive and replaced them in the spring.

Since then, the hotel has changed how it waters its palm trees to prevent freeze damage. The palm trees won't be covered during this weekend's chill, but Monet predicted they would survive if temperatures didn't dip below the mid-20s and the cold weather didn't last long.

At least one provider for the homeless plans to offer a few extras to help fight off the cold this weekend.

Catholic Charities of Southern Nevada plans to keep its dining room open all day, offering coffee and hot soup to shivering souls.

But it's going to be tougher at night.

The agency opened a winter shelter in November with room for 200 men. It isn't enough.

"I can tell you we're averaging 380 men a night, with beds for 200," said Sharon Mann, a spokeswoman for the agency. "The other 180 are sleeping on the floor."

The agency turns the dining room into a makeshift shelter for women at night.

The Salvation Army shelter, with room for 550 people, has been full every night for weeks and has no additional space set aside especially for cold weather, a spokesman said.

"We're using the floors now," Charles Desiderio said. "We're maxed out."

Desiderio said overcrowding at local shelters is common during the hottest and coldest parts of the year.

Clark County does have a cold weather plan designed to take effect when extreme weather hits and shelters fill up.

The county might open a recreation center or other facility as a shelter and staff it until the extreme cold passes, said Michele Fuller-Hallauer, the Continuum of Care coordinator for the Southern Nevada Regional Planning Coalition's Committee on Homelessness.

"It's not elaborate -- two blankets, water and a granola bar," she said about the proposed operation. "But it will keep them out of the cold."

Fuller-Hallauer said the county plans to have a meeting today to decide whether to offer additional shelter space.

"We're on standby," she said. "We're getting everything ready."

Review-Journal staff writers Paul Harasim and Lynnette Curtis contributed to this report.