(CNN) -- Texas is colder than it has been in decades and is one of at least 25 states under a winter weather advisory during this week's historic cold spell.
But as Texans struggle to stay warm, power outages have begun across the state due to high demand.
Millions of customers across the US have lost power, and most of those outages are in Texas. Power outages can be dangerous for those who are not prepared for such intense winter cold.
If you're in the middle of a power outage or expect one to happen sometime this week, here's what you need to know to stay warm and safe.
Stay home
Staying indoors is the best way to stay safe during a winter power outage, says the U.S. Centers for Disease Control and Prevention. its acronym in English).
If you can, stay off the roads; Icy conditions can lead to car accidents. Last week, at least nine people were killed in car crashes sparked by winter storms in the Dallas-Fort Worth area, including six who died in the 133-car pileup in Fort Worth.
Take stock of the essentials
In case the power outage lasts a few days, you should have the following on hand:
If you need to take a trip outside, keep it as brief as possible and wear several layers of clothing, says the CDC. Check with your local emergency authorities to make sure it is safe to drive or ride in the cold.
Stay warm
Wear several layers of clothing, it's going to be cold. In extremely cold conditions, the Houston Office of Emergency Management recommends wearing at least three layers of tops, plus an outer layer to block the wind, and two layers of pants. A hat, gloves, and a warm face mask are also a must.
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The CDC recommends warming up with extra blankets, sleeping bags, and winter coats.
However, it is not safe to keep blankets and other flammable materials near alternative sources of heat, such as a space heater. Keep heaters in an area free of flammable fabrics.
If you use a fireplace, first make sure it has adequate ventilation to the outside and that there are no gas leaks into your home. You should keep it stocked with dry firewood, not paper, the CDC says, during the power outage.
To keep in the heat, close blinds and shades and close bedroom doors to avoid "wasting heat," recommends the National Weather Service. Placing towels in the gaps under doors can prevent the cold from entering your home, and eating and drinking during the power outage will help keep your body warm.
Take care of your food and water supply
Avoid opening your refrigerator or freezer during the power outage to keep food cold. According to the Federal Emergency Management Agency (FEMA), a refrigerator can keep food cold during a power outage for approximately four hours, and a freezer will maintain its temperature for approximately 48 hours.
Fill coolers with ice, if necessary, to prevent food from spoiling.
Some water purification systems may not fully function when the power goes out, the CDC warns. You can check with local officials to make sure the water is safe; they should give specific recommendations for water treatment in your area.
Watch out for carbon monoxide
Generators can release poisonous carbon monoxide if used inside your home. If you're using one this week, keep it outside, about 20 feet from your home, the CDC advises.
You should never use a gas stove or oven to heat your home, according to Ready.gov, the US government's online disaster planning resource.
If it's safe, move to a warm place
If it's safe to travel to a shelter, be sure to wear a mask or two-layer mask and pack extra in case you stay longer. These locations should be well ventilated, though social distancing is still recommended, according to Ready.gov.
Know the Signs of Hypothermia
Infants, older adults, and the homeless are most vulnerable to hypothermia. If you're worried about people in these groups, look for the signs: confusion, chills, slurred speech, sleepiness and muscle stiffness in adults, and bright red skin and low energy in babies, according to the CDC.
If you fear someone in your home may be hypothermic, seek medical help. If they can't get to it right away, try to keep them warm with blankets, food and water, and an alternate heat source.
Save energy if you still have it
Start by turning off and unplugging lights and nonessential appliances, and skip large appliances like ovens or washing machines if you can avoid it, suggests the Office of Emergency Management of Houston.
Turn your thermostat down to 68 degrees or below; if too many people turn up the heat, the demand could trigger another blackout.
During the day, if it's sunny, open the blinds to let the sun warm your house, but close them at night to avoid losing heat.
Call loved ones
When it is safe to do so, check with the people around you to make sure they are okay.
Those who have medical equipment that requires power, such as ventilators, should be taken to places with generators or to a friend or neighbor's house that has not been affected.
Take care of your pets
Don't leave pets outside when it's cold. Move them to a shelter indoors where they're warm, advises the Humane Society of the United States.
If you take your dog for a walk (although the outdoor activity should be brief), consider wrapping him in a sweater or coat; pets can also get hypothermia.
Look on your pet's paws for rock salt or other chemicals used to melt ice. Those chemicals can irritate your pet's paws, so wipe them off with a warm, damp towel when you get home.
If you have a reptile or other pet that relies on external heat sources, you can do so with hand warmers, a generator (again, use only outside your home), or snuggling, says PetCoach, a veterinary database at Petco line.
