It can attack your fingers and toes, render your car useless and cause costly damage to your home.
After yet another bout of snow, bitter cold is expected to settle over the suburbs in the coming days, and it's not only unpleasant -- it can be dangerous.
National Weather Service forecasters expected snow accumulation of 5 to 10 inches by Sunday, followed by cold air moving in from the north that will create a near-record-breaking freeze on Monday.
Wind chills are expected to fall as low as 10 to 20 below zero by tonight, dropping further to 40 below zero by Monday morning.
The lowest recorded high for that day is minus 11 degrees, a record set in 1983 and matched in 1994. And forecasters say 2014 could get close with predicted highs of 8 below zero Monday. Tuesday's temperatures could remain below zero as well, leaving suburbanites with no respite from subzero temperatures that will start Sunday night.
Dr. Douglas Propp, emergency room medical director at Advocate Lutheran General Hospital in Park Ridge, says people shouldn't go outside unless they have to and should cover all exposed skin if they do, as the cold can damage skin in "minutes." Quickly dropping temperatures could be particularly dangerous for people with respiratory issues.
Still, emergency rooms might not be packed if the frigid temperatures keep people indoors, he said.
"If people are frightened by the temps and heed the recommendations, we might not be," Propp said.
Cars are also vulnerable to the cold, and owners should take precautions.
Mike Bruens, co-manager of Casey Automotive in Arlington Heights, said people should make sure they have a good car battery, good wiper blades and a full tank of washer fluid before temperatures drop.
Car batteries last three to four years, he said. Older ones often won't start a vehicle in such cold weather.
"They aren't usually coming in by choice at that point," Bruens said of his customers. "A lot of tow trucks will be coming in."
Keeping the gas tank more than half full during subzero temperatures is also a good idea, he said.
Whether you are venturing out or just hunkering down, your home needs extra care -- starting with the furnace.
"Proper maintenance is critical," said Ron Magrini, co-owner of 24HR Home Comfort Services in Lake in the Hills. "There's a lot of people that think it works like magic. It's kind of like, 'Out of sight, out mind.'"
Filters need be replaced regularly, Magrini said.
Magrini also advises making sure your furnace humidifier is working properly. If you don't have one, it's not too late to get one, although it can cost about $650.
"It's worth every penny," Magrini said.
Humidifiers add moisture to the warm air circulated by the furnace. Dry air makes the temperature feel colder, dries out wood trim and can cause nose bleeds, Magrini said.
Stand-alone humidifiers in the house will also help with dry air. And there's nothing wrong with simply boiling some water on the stove, he said.
"The house will feel warmer with more humidity, but you don't want too much that you get moisture on the windows," he said. "There's a fine line there."
Some furnaces are vented via exterior PVC pipes, so it's important to make sure those pipes aren't frozen, he said.
Water pipes also need protection against freezing and potentially bursting. George Swietczak, a plumbing inspector for the village of Lake Zurich with 52 years in the industry, said boosting the thermostat up to 80 degrees typically won't result in a home becoming that warm in a deep freeze, but it will protect pipes in areas that might be chilly inside. For a 2,000-square-foot home, he said, the added heating cost may be $25 or $30 over four days.
"Factor that against a $500 or more plumbing bill or damage," Swietczak said.
In cool or poorly insulated areas, Swietczak said water should be left to run from a faucet in a small, thin stream -- not drips. He said the extra water cost is preferable to the damage and expense from burst pipes.
Swietczak said caution must be exercised to thaw frozen pipes.
"If the water line freezes, a hair dryer is the safest device," he said.
Gurnee's Charles E. Crowley Jr., founder of C.E. Crowley and Associates Inc., said homeowners should be proactive in trying to prevent roof problems that can develop from prolonged below-zero temperatures and heavy snow.
Homeowners should protect against ice damming that starts at the edge of a roof and creeps upward. He said they can do that by making sure attic vents in the roof are open and breathe and are not plugged by insulation.
Crowley said not to worry much about icicles, because removal may cause damage. If icicles pose a potential risk hanging over a doorway or similar spot, minimum force should be used to knock them off.
When spring arrives, homeowners should inspect their roof -- particularly if it is 12 years or older -- for potential damage after a severe winter occurs, Crowley said.
A ComEd spokeswoman says the utility doesn't expect significant issues in the system as a result of the deep freeze, but it has beefed up its staff in case problems do occur.
If people have problems with service, spokeswoman Martha Arendt advises texting "OUT" to 26633 or calling (800) 334-7661.
"We are monitoring the situation closely," Arendt said. "We're ready to respond if needed and certainly encourage everyone to stay safe out there."
• Daily Herald staff writers Bob Susnjara, Melissa Silverberg, Elena Ferrarin and Lenore Adkins contributed to this story.