National Weather Service United States Department of Commerce

Winter Weather Infographics


Snow Ratio: The percentage of water within a sample of snow is called 'snow ratio'. An old rule of thumb was that for every to inches of snow, there would be 1 inch of water (10:1). However, snow ratios can vary dramatically around the country and from event to event.
Variables that affect snow ratio: 1) Depth of the 'warm' layer from the surface into the snow-producing cloud. Amount of ice in the snow-producing cloud. If its windy, snowflakes can fracture, losing their 'lacy' structure. Deep cold leads to higher snow ratios.
Snow Squall: An intense, but limited duration period of moderate to heavy snowfall, accompanied by strong, gusty surface winds and possibly lightning. Snowfall rates may be significant. Hazard: Heavy snow and blowing snow, wind gusts up to 40 mph. Source: Radar indicated. Impact: Dangerous life-threatening travel. What you can do: Try to safely exit the highway, drive slowly, increase your following distance.
Winter Precipitation:
Snow: Snowflakes never melt
Sleet: Droplets freeze and form ice before reaching the surface
Freezing Rain: Rain freezes on contact with the surface
Rain: Rain never refreezes
Snow Water Cycle: The hydrologic cycle involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground to the atmosphere and back again. During the winter months, falling snow serves as an important source of fresh water across the world. When spring arrives, melting snow helps replenish rivers, lakes and reservoirs. The melting snow adds much needed moisture to the soil and helps refill underground aquifers, which are vital for growing crops and for drinking water.
Infographic - The Science of Wind Chill. The average temperature of the human body is 98.6 degrees fahrenheit. Under calm conditions, the body radiates heat, creating a layer of warmth between or skin and the cold surroundings.  But when it's windy, the moving air breaks up this insulating layer. It speeds up heat loss by whisking away the warmth from our skin. Hypothermia begins when our body temperature drops two to four degrees.
The Science of Vallery Fog: 1. Air cools at higher elevations as the ground radiates heat into the atmosphere and space. 2. Cooler air drains downslope into the valley. 3. A cool, stable layer forms the ground, which limits turbulent mixing and traps the cool, moist air.  4. The air near the ground continues to cool until water vapor moleculesd are changed into small droplets of liquid water.
Winter's Fury - Colorado Low: There's nothing more wintry than a Colorado low, which spins up on the east side of the Rockies. From Denver to Chicago -- or Cleveland to Pittsburg, if forecasters are calling for a foot of snow, there's a decent chance a Colorado low is the culprit.
Winter's Fury - Alberta Clipper: As their name suggest, these fast-moving low pressure systems get their start in Canada and zip across our northern states. They can pack a punch with a narrow band of 'dry' but significant snow. In the winter, these systems commonly bring in below zerp temperatures and are often responsible for white-out conditions from Montana to the Dakotas.
Winter’s Fury - Nor’easters: Not many winter storms have the potential to bury 100 million people in 1-2 feet of snow in a single day. Nor'easters are notorious for packing big wind and copious amounts of moisture they get from the Atlantic. The heavily populated region between Washington D.C., Philadelphia, New York and Boston, the 'I-95 Corrdior', is epsecially impacted by Nor'easters.
Winter's Fury - Gulf of Alaska Lows: Large temperature differences across the Pacific and strong Coriolis Force, due to the high latitude, combine to create some of the strongest storms on the face of the Earth. Wind speeds can exceed 100 mph and produce 30+ ft waves as the central pressure of these storms can be as low as major hurricanes.
Warnings signs of hypothermia: confusion, shivering, difficulty speaking, sleepiness, stiff muscles.
Infographic - Closing for Cold
Getting Traction - Tips for Traveling in Winter: Pack an emergency supply kit. Winterize your vehicle. Check the NWS forecast. Check road conditions. Have your mobile device on hand.
Winter Travel Forecasts: By Land - By Sea - By air -
Dressing for the Cold - Infographic. Adding layers will help keep you warm as the temperature drops. Chilly: 1-2 layers; outer layer to keep out wind, rain; long layer on legs; warm shoes (water proof). Cold: 2-3 layers; warm hat; gloves; outer layer to keep out wind, wet snow; 1-2 long layers on legs; boots (water-proof). Extreme cold: 3+ layers (1 insulating); warm hat; face mask; gloves; outer layer to keep out wind; 2+ long layers on legs; boots (water proof).
Six Basic Steps for Properly Measuring Snow - Accurate and timely snowfall measurements are extremely important to your National Weather Service office, your community, local media, and many others. Here are the six steps you need to know for measuring snow: 1) Supplies - Ruler or yard stick, 24 x 24 inch white board, flag. 2) Planning - Find an open area away from tall objects, but sheltered from wind. 3) Set-up - Set up before snow begins. Put your board out and mark it with the flag. 4) Measuring snow - Record your toal to the nearest tenth of an inch. Wipe the board off after measuring. Measure with ruler once daily at the same time, after measuring place the board on top of snow. 5) When Snow Stops - Measure as soon as the snow stops to avoid lower totals due to melting, settling and drifting. 6) Reporting - Send us your report via or social media!
5 Tips for Shoveling Snow Safely: 1) Get the latest forecast. 2) Push don't lift. 3) Wear breathable clothes. 4) Wear warm boots. 5) Drink water.
Blizzard Warning: Severe winter weather is expected within the next 12 to 36 hours or is occurring - including whiteout conditions. Do not travel. TAKE ACTION. Winter Storm Warning: Dangerous winter weather is expected within the next 12 to 36 hours or is occurring. Considerable travel problems are expected. TAKE ACTION. Winter Weather Advisory: Potentially dangerous winter weather is expected within the 12 to 36 hours or is occurring. Travel difficulties are expected. BE AWARE.
Winter Storms - Stay ahead of this storm by following the watches and warnings issued by the National Weather Service.
Outdoor Winter Safety - Use caution when you head outside to work or to play. Each year, emergency rooms in the U.S. treat thousands of injuries related to sledding, ice skating and shoveling.
Fire Safety - Be diligient during this incoming winter storm, our heating, lighting, and cooking activities increase the risk of residential fires.
Indoor Winter Safety - Check your smoke/carbon monoxide (CO) detectors. The danger of CO poisoning is greater during winter storms when doors and windows stay closed and fireplaces and gas heaters are in use. You can also be exposed to deadly CO levels when 'warming up' your car in the garage or when snow covers your tail pipe.
Winter Driving - Slow down and use caution if you must travel during this upcoming winter storm as road conditions can change quickly. Before you travel, pack a winter survival kit for your vehicle. If possible, consider altering your travel plans.
What is Freezing Rain? Freezing rain is liquid precipitation that freezes on contact with cold surfaces as it enters a shallow layer of temperatures at or below 32 degrees F near the surface. This creates a dangerous coating of ice on roads, walkways, trees and power lines. Precipitation in the atmosphere starts off frozen as snow. Snowflakes melt as they fall through warm air. Droplets freeze as they enter a shallow layer of air at or below 32 degrees near the surface.
What is Freezing Rain? Freezing rain is liquid precipitation that freezes on contact with cold surfaces as it enters a shallow layer of temperatures at or below 32 degrees F near the surface. This creates a dangerous coating of ice on roads, walkways, trees and power lines. 1) Ice accumulation increases the weight of a span of powerlines by up to 500 pounds! 2) Patches of ice on roads and highways make traveling extremely dangerous. 3) Ice accumulation increases the weight of a tree by 30 times!
5 Things to Know about Winter Weather Forecasts: 1) Snow or ice totals can vary greatly over short distances. A heavy snow band my form, dropping more snow in one location while significantly less snow falls just a few miles away. 2) Winter forecasts can change frequently. Forecasts may change as new model data becomes available. Always check for the latest information. 3) Focus more on the winter storm's impacts. Don't focus too much on exact numbers and consider the full range of possibilities. 4) Know your winter weather terminology. If a Watch is issued, get prepared for hazardous weather. If a Warning or Advisory is issued, take action - hazardous weather is occuring or will occur soon. 5) Rely on a dependable source for weather info. Choose your information sources wisely, and follow a name or organization you know and trust.
Winter Driving: Each year, weather-related crashes cause more than 6,000 deaths and 480,000 injuries. If the outside temperature is near freezing, drive like you're on ice. You may be!

10 Fun Facts About Snow

10 Fun Facts About Snow: #1. All snowflakes have six sides.
10 Fun Facts About Snow: #2. An incredible 1,140 inches (95 feet) was recorded at Mount Baker Ski Area in Washington State (4,200 feet elevation) during the July 1, 1998 to June 30, 1999 snow season.
10 Fun Facts About Snow: #3. The most snow measured in 24 hours was 75.8 inches, which fell in Silver Lake, Colorado, April 14-15, 1921, enough to bury most people from head to toe.
10 Fun Facts About Snow: #4. Snow crystals are translucent, not white. The white coloring is caused by sunlight that is reflected off the crystals. All visible colors are reflected, which together, look white.
10 Fun Facts About Snow: #5. Most snowflakes fall at a speed of 2 to 5 feet per second, roughly the same speed as a person casually walking through a park.
10 Fun Facts About Snow: #6. Official snowfall and snow depth measurements include snow, sleet and ice pellets - in the summer, hail will also be recorded as a trace of snow if it is on the ground when the observation is taken.
10 Fun Facts About Snow: #7. Did you know a blizzard can occur without falling snow? If wind speeds remain higher than 35 mph and the visibility is also reduced to less than 1/4 mile for three hours or more, then it's classified as a blizzard.
10 Fun Facts About Snow: #8. A cubic feet of snow (12 inches on a side) may contain between 1 and 2 million individual snowflakes.
10 Fun Facts About Snow: #9. Thundersnow is simply a thunderstorm with snow as the precipitation type. It typically occurs where there is really strong upward motion inside a winter storm.
10 Fun Facts About Snow: #10. All 50 states have recorded snowfall. In Hawaii, snow is observed on the tallest volcano summits every year, and light snow (mainly trace amounts) is an almost yearly occurrence in northern Florida.