Learn how these winter snowstorms form—and how you can stay safe if one blows your way.

The temperature outside is below freezing, the winds are howling, and you can barely see the tree in your front yard. A large amount of snow has been falling for more than three hours—a blizzard is under way.

According to the National Weather Service, blizzards are snowstorms with winds higher than 35 miles an hour and visibility (meaning, how far you can see) of less than a quarter mile. Winds from a blizzard can travel over 120 miles an hour—that’s faster than a cheetah, the world’s fastest land animal.

These conditions can be dangerous—low visibility can cause drivers to crash on roads, and high winds can topple power lines, which means some homes will be without heat. Large amounts of snowfall can trap people inside their homes. And those stuck outside in freezing temperatures can face frostbite or hypothermia, a condition in which your body temperature becomes dangerously low.

Learn more about these dangerous winter storms—and what to do if one comes your way.

How blizzards develop

Before you can have a blizzard, you first need snow. And for snow, you need clouds.

Clouds form when part of the air becomes cold enough that water vapor, which is the gas form of water, condenses and becomes tiny water droplets that form around things like dust and sea salt. When those droplets collect more water, they fall as rain. At temperatures between about minus 40°F and 32°F, the water droplets crystallize. When enough crystals stick together, they form snowflakes and fall to the ground.

What makes a snowstorm a blizzard is strong wind. First, warm air from the Equator mixes with cold air from the Arctic. Wind forms when warm air rises over the cold air; the faster the warm air rises over the cold air, the stronger the wind becomes.

Another type of winter storm is called a ground blizzard. This is when gusty winds—often 50 to 60 miles an hour—lift up snow that’s already on the ground. Both types of blizzards can cause whiteouts, a condition in which so much snow is blowing so fast that it’s hard to see anything. Sometimes you can’t even tell the difference between the sky and the ground!

Blizzards in the future

Blizzards occur all over the world. But because they’re closer to the Arctic, places like Russia, central and northeastern Asia, northern Europe, Canada, and the northern United States experience more blizzards than other parts of the globe.

And though most blizzards occur during winter, they can happen during other seasons, too. One of the most severe blizzards in the United States—known as the Great Blizzard of ’88—happened in March 1888, killing more than 400 people.

Scientists believe that as global temperatures continue to rise because of climate change, blizzards could become more extreme. A warmer atmosphere means more moisture in the air that will eventually fall as snow (or rain); many also believe that warmer temperatures will create higher winds.

How to survive a blizzard

The best way to survive a blizzard is to prepare for extreme weather. Meteorologists use certain words and phrases that will help you know when a blizzard is coming. For instance:

Wind chill factor: This is what the temperature feels like outside, even if the real temperature is higher. Blizzards usually have wind chill factors of 10°F or lower.
Winter storm outlook or watch: This means that conditions are right for a snowstorm or blizzard to form.
Winter weather advisory: This means that dangerous winter weather is happening, which could be a blizzard.

Learn more about ways you can protect your family from dangerous winter weather.

Before a blizzard:

• Ask your parents to "winterize" your house: Check that heating sources are clean and working, and make sure windows are insulated so cold air can’t come in. (If they’re not, apply plastic sheets on the inside.)
• If you have a fireplace, stock up on firewood or coal.
• Make sure your family has a home emergency kit: water (at least a gallon for each person per day for several days), food (non-perishable or canned items for several days), flashlight, extra batteries, first-aid kit, manual can opener, local maps, battery-powered radio, and cell phone with a backup battery.
• Charge devices like cell phones.

During a blizzard:

• Listen to local radio or news for updated weather information.
• Layer up if you lose power. Try a t-shirt under a long-sleeved shirt under a sweater under a coat. That way you can take off items if you start to sweat. (Being cold and wet will just make you colder!) Other must-haves: two pairs of socks, mittens instead of gloves, a thick scarf, and a hat.
• Drink lots of water—or hot cocoa, or tea, or whatever—to stay hydrated. You might not think you need as much liquid in the winter as you do in summer, but staying hydrated helps your body generate enough heat to maintain a healthy body temperature.
• Evacuate only if you lose power and your home becomes too cold to stay in. Try to find a shelter—like a nearby school or library—that has heat and electricity.

If you must leave your house:

• Try to travel during the day when visibility will be better.
• Load up on blankets, canned fruits, bottles of water, and warm fluids in a thermos; bring an external battery in case you need to recharge your cell phone.
• Don’t forget the layers!
• If you get stuck in your car, huddle with your companions for extra warmth.
• If you’re caught outside, huddle together against a tree or a rock ledge to block the wind, and do not sit down on snow. (Your non-frozen butt will thank you.) And don’t eat the snow—that could dangerously lower your body temperature.
• If you or your companions show signs of hypothermia or frostbite (shivering, feeling very tired, confusion, drowsiness, memory loss, slurred speech), seek help immediately.