If traveling by air:
First the good news: Your plane is certified to fly in "extreme conditions," according to Boeing spokesman John Dern—probably far more extreme than anything a snow storm can throw your way.
The Federal Aviation Administration (FAA) has a long list of flight requirements for commercial aircraft, which manufacturers generally exceed. Many of the rules are designed to ensure that your plane can operate in wind and snow.
Weather-related flight cancellations seldom happen because a plane can't handle the prevailing conditions, according to veteran airline captain and aviation analyst John Nance. "Usually your flight can't operate because the airport shut itself down, or the airline decided to ground a large number of flights for operational reasons," he says.
Which brings us to the bad news: Just the anticipation of problems and long delays can spur airlines to cancel.
What are the factors going into such decisions? Each weather condition presents different dangers or difficulties:
In clear weather, winds are rarely a factor, and then only if they're blowing across, not down, the runway. "If you have a dry runway, you can take a crosswind of 25 knots in many commercial aircraft," says Nance.
But in rain or snow—or any condition that slickens the runway—tolerance for a crosswind decreases. It becomes that much harder for a pilot to stay on the centerline of the runway without skidding, particularly when landing a large plane at 150 miles an hour. Brakes are the vital element, because a pilot can't bring a plane to a stop using reverse thrust alone.
Each airline has FAA-approved formulas and tables it uses to determine the maximum crosswind. If a severe winter storm hits and causes ice on the runways, even a moderate crosswind could exceed the limits and make a takeoff or landing unsafe.
"You can reach the point that even a five-knot crosswind could blow you off a frictionless ice-covered runway," says Nance.
Light or moderate snow will not stop operations, says Nance. "A heavy snowfall, however, can cause cancellations."
Even planes that have been de-iced need to reach the runways, which often require heavy plowing.
Pilots could face difficulties generating flying speed in slush, standing water over a half-inch deep, or when there's too much snow accumulation. In such conditions, the drag on the aircraft tires can be so great that a plane is unable to take off before the runway ends. Visibility can also be a factor.
Bottom line? A few snowflakes won't cause a cancellation, but a blizzard might.
"One thing we don't fly in is freezing rain," says Nance. "If an airport is hit with rain or drizzle when temperatures hover near the freezing point, airport authorities will consider shutting it down and most definitely the airlines will start canceling flights."
The reason? In such conditions, aircraft can gather ice faster than de-icing equipment can remove it, and ice can also wreak havoc on every other part of airport operations. An aircraft can lose traction in the ice, making it difficult to control. Critical equipment can freeze, and braking can become uncertain if not impossible.
Airlines, airports, and the FAA do what they can to prevent weather from stranding passengers, but their strategies have changed in the last few years, particularly in light of the Department of Transportation's 2009 rules on airport-tarmac delays, which fine airlines for keeping passengers on a parked plane for more than three hours.
"It's better to inconvenience a passenger at their point of origin," says Nance. "Having a sky full of airplanes that can't land and are sucking up fuel is not a good strategy."
Stay on main roads and highways, and stick to the flattest roads you can. Avoid hills and roads with sloping surfaces when possible.
Drive only during daylight hours, and avoid driving alone if you can.
Bring blankets with you to keep warm in case you become stranded. Also bring bottled water or warm beverages, to avoid becoming dehydrated.
Let family members know where you're going and when you're expected to return.
If a snowstorm or blizzard forces you to stop, pull off the highway and turn on your hazard lights. If you have a distress flag or sticker, hang it from your radio antenna or apply it to your window. Remain in your car, where rescuers are most likely to find you.
If you're stranded for an extended period of time, run your engine for about 10 minutes every hour to stay warm. Open a window slightly for ventilation while the car is running, to prevent any carbon monoxide buildup. Remove any snow that builds up on your car's exhaust pipe.
If you have to spend the night in your car, turn on the interior overhead light so rescuers or work crews can see you.
Before driving make sure you check or have a mechanic check the following items on your car:
• Antifreeze levels - ensure they are sufficient to avoid freezing.
• Battery and ignition system - should be in top condition and battery terminals should be clean.
• Brakes - check for wear and fluid levels.
• Exhaust system - check for leaks and crimped pipes and repair or replace as necessary. Carbon monoxide is deadly and usually gives no warning.
• Fuel and air filters - replace and keep water out of the system by using additives and maintaining a full tank of gas. A full tank will keep the fuel line from freezing.
• Heater and defroster - ensure they work properly.
• Lights and flashing hazard lights - check for serviceability.
• Oil - check for level and weight. Heavier oils congeal more at low temperatures and do not lubricate as well.
• Thermostat - ensure it works properly.
• Windshield wiper equipment - repair any problems and maintain proper washer fluid level.
• Install good winter tires - Make sure the tires have adequate tread. All-weather radials are usually adequate for most winter conditions, however some jurisdictions require that to drive on their roads, vehicles must be equipped with chains or snow tires with studs.
Know the terms used to describe changing winter weather conditions and what actions to take. These terms can be used to determine the timeline and severity of an approaching storm. (Advisory / Watch / Warning). Be alert to weather reports and tune in for specific guidance when these conditions develop.
Freezing Rain - Rain that freezes when it hits the ground, creating a coating of ice on roads, walkways, trees and power lines.
Sleet - Rain that turns to ice pellets before reaching the ground. Sleet also causes moisture on roads to freeze and become slippery.
Wind Chill - Wind chill is the temperature it “feels like” when you are outside.
Winter Weather Advisory - The National Weather Service (NWS) issues a winter weather advisory when conditions are expected to cause significant inconveniences that may be hazardous. If caution is used, these situations should not be life-threatening.
Winter Storm Watch - A winter storm watch is issued 12 to 36 hours in advance of a potential severe storm. Tune in to Weather Radio, local radio, TV, or other news sources for more information. Monitor alerts, check your emergency supplies, and gather any items you may need if you lose power.
Winter Storm Warning - A winter storm is occurring or will soon occur in your area.
Blizzard Warning - Sustained winds or frequent gusts to 35 miles per hour or greater and considerable amounts of falling or blowing snow (reducing visibility to less than a quarter mile) are expected to prevail for a period of three hours or longer.
Frost/Freeze Warning - Below freezing temperatures are expected.
Caution: Each year, many individuals die from unintentional carbon monoxide poisoning, and there are more and more visits to the emergency room with more hospitalizations. Carbon monoxide-related deaths are highest during colder months. These deaths are likely due to increased use of gas-powered furnaces and alternative heating, cooking, and power sources used inappropriately indoors during power outages.
• Never use a generator, grill, camp stove or other gasoline, propane, natural gas or charcoal burning devices inside a home, garage, basement, crawlspace or any partially enclosed area. Locate the unit away from doors, windows and vents that could allow carbon monoxide to come indoors. Keep these devices at least 20 feet from doors, windows, and vents.
• The primary hazards to avoid when using alternate sources for electricity, heating or cooking are carbon monoxide poisoning, electric shock and fire.
• Install carbon monoxide alarms in central locations on every level of your home and outside sleeping areas to provide early warning of accumulating carbon monoxide.
• If the carbon monoxide alarm sounds, move quickly to a fresh air location outdoors or by an open window or door.
• Call for help from the fresh air location and remain there until emergency personnel arrive to assist you.