Winter Storm Watch vs Warning: What’s the Difference?

By
Harris
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21

Key Points

  • A Winter Storm Watch means a significant winter storm is possible. A Winter Storm Warning means heavy snow, sleet or ice is occurring or expected. The National Weather Service (NWS) sums it up as “Be Prepared” versus “Take Action.”
  • The NWS glossary says watches usually come at least 24 to 36 hours ahead, while Ready.gov (FEMA) says watches usually arrive 12 to 48 hours before a storm and warnings 12 to 24 hours before.
  • There is no single national snowfall number. Each NWS office sets local criteria, so a warning in the Southeast can take far less snow than one in the Northern Plains.
  • A Winter Weather Advisory (“Be Aware”) sits one step below a warning, and a Blizzard Warning is a separate alert driven by wind and visibility, not snowfall.
  • Since Oct. 1, 2024, the NWS has used Extreme Cold Watch, Extreme Cold Warning and Cold Weather Advisory in place of the old wind chill alerts.

Winter storm watch vs warning: what is the difference? A watch means a significant winter storm is possible and you should get ready. A warning means the storm is happening or is expected, and you should act now to stay safe. The National Weather Service labels the two tiers “Watches: Be Prepared” and “Warnings: Take Action!”

This guide explains what each alert means, how much lead time to expect, why snowfall thresholds change from city to city and how advisories and other winter alerts fit in, using definitions from the NWS, its local forecast offices and Ready.gov.

Winter Storm Watch vs Winter Storm Warning at a glance

Alert What it means Typical timing What to do
Winter Storm Watch Conditions are favorable for a significant winter storm (heavy snow, heavy sleet, significant ice or a combination) Usually at least 24 to 36 hours ahead (NWS glossary); 12 to 48 hours ahead (Ready.gov) Be prepared: check supplies, plan travel, monitor updates
Winter Storm Warning A significant winter storm with heavy snow, sleet, ice or blowing snow is occurring or forecast Usually 12 to 24 hours before the storm begins (Ready.gov) Take action: delay travel, stay home if you can
Winter Weather Advisory Snow, sleet, freezing rain or a mix is expected but below warning criteria Varies by office Be aware: use caution and expect slow travel

Source: National Weather Service, Winter Weather Warnings, Watches and Advisories; NWS Glossary; Ready.gov Winter Weather.

What is a Winter Storm Watch?

According to the National Weather Service, a Winter Storm Watch is issued “when conditions are favorable for a significant winter storm event,” which the agency describes as heavy sleet, heavy snow, an ice storm, heavy snow with blowing snow, or a combination of those hazards. The NWS glossary adds that a watch is issued when there is a potential for heavy snow or significant ice accumulations, “usually at least 24 to 36 hours in advance.”

Ready.gov, the federal preparedness site run by FEMA, describes the same alert as one that “alerts the public to the possibility of a blizzard, heavy snow, heavy freezing rain, or heavy sleet,” and says watches are usually issued 12 to 48 hours before a storm begins.

The key word is possibility. A watch goes out while forecasters still have real uncertainty about the storm’s track, timing or precipitation type. The NWS office in Milwaukee/Sullivan, Wisconsin, explains on its winter terminology page that there is often uncertainty with the path or impacts of an upcoming storm, and that a watch is upgraded to a warning when the nature and location of the event become more apparent. A watch can also be canceled if the storm shifts away, or replaced with a lower-level advisory if the storm turns out weaker.

What is a Winter Storm Warning?

The NWS says Winter Storm Warnings are issued “for a significant winter weather event including snow, ice, sleet or blowing snow or a combination of these hazards,” and warns that travel “will become difficult or impossible in some situations.” Its glossary describes the warning as a product issued when a winter storm “is producing or is forecast to produce heavy snow or significant ice accumulations.”

Ready.gov says a warning is issued when hazardous winter weather “is imminent or occurring” and that warnings are usually issued 12 to 24 hours before the event is expected to begin. Its advice is blunt: if you are under a Winter Storm Warning, find shelter right away.

Why the snowfall threshold changes from place to place

There is no single national number of inches that triggers a warning. The National Weather Service says winter watches, warnings and advisories are issued by your local NWS office based on local criteria, and gives an example: the amount of snow that triggers a Winter Storm Warning in the Northern Plains “is typically much higher” than the amount needed in the Southeast.

Local NWS offices publish their own criteria. A few examples from official NWS pages:

  • Chicago (NWS Chicago): a Winter Storm Warning is used when 6 inches or more of snow in 12 hours, or heavy sleet of one half inch or more, is expected. The office says a warning may also be issued for lower totals if conditions approach blizzard criteria or impacts are significant.
  • South-central and southeast Wisconsin (NWS Milwaukee/Sullivan): warnings are usually reserved for heavy snow exceeding 6 inches in 12 hours or 8 inches or more in 24 hours, according to the office, and may be issued for smaller amounts if the bulk of the snow falls during rush hour or with strong winds.
  • Eastern Washington and northern Idaho (NWS Spokane): the office lists warning thresholds that range from 4 inches to 12 inches of snow or sleet during an event, depending on the forecast zone.

A warning means your local forecasters expect conditions that are significant for your area, so do not compare it with an alert in another state.

Winter Weather Advisory: one step below a warning

The NWS issues a Winter Weather Advisory when snow, blowing snow, ice, sleet or a combination is expected “but conditions should not be hazardous enough to meet warning criteria.” The agency’s message for advisories is “Be Aware,” and it tells drivers to be prepared for winter driving conditions and possible travel difficulties.

Advisories still matter. Ready.gov says a Winter Weather Advisory covers accumulations of snow, freezing rain, freezing drizzle and sleet that will cause significant inconveniences and, if caution is not exercised, could lead to life-threatening situations.

Other winter alerts you may see

According to the NWS winter alerts page, other common winter alerts include:

  • Blizzard Warning: issued for frequent gusts of 35 mph or more with falling or blowing snow frequently reducing visibility to less than 1/4 mile for three hours or more. The NWS advice is “Do not travel.” Our explainer on what makes a storm a blizzard covers the full definition.
  • Ice Storm Warning: usually issued for ice accumulation of around 1/4 inch or more, which the NWS says will make travel dangerous or impossible and likely lead to snapped power lines and falling tree branches.

If you are unsure how sleet differs from freezing rain, both of which can trigger these alerts, see our guide to sleet vs freezing rain.

The new names for cold alerts

Some older guides still list Wind Chill Watches, Warnings and Advisories. The NWS announced that starting Oct. 1, 2024, Wind Chill Watches were renamed Extreme Cold Watches, Wind Chill Warnings became Extreme Cold Warnings and Wind Chill Advisories became Cold Weather Advisories. The agency said the change was meant to clarify that cold can be dangerous with or without wind. Wind chill itself has not gone away; our explainer on how wind chill works explains the calculation.

What to do when a Winter Storm Watch is issued

A watch is your window to prepare while stores are open and roads are clear. The NWS winter preparedness page says your main concerns at home or work during a winter storm are loss of heat, power and telephone service, plus a shortage of supplies if the storm lasts more than a day. The agency recommends having:

  • A flashlight and extra batteries
  • A battery-powered NOAA Weather Radio or portable radio for emergency information
  • Extra food and water that needs no cooking or refrigeration
  • Heating fuel, topped up before you run low, because the NWS notes fuel carriers may not reach you for days after a storm
  • A working smoke alarm, fire extinguisher and carbon monoxide detector

The NWS also says to check that your vehicle’s fluids, lights, heater and windshield wipers are in good condition, to keep the gas tank near full and to call 511 for state road conditions before a trip. It also says never to run a generator in an enclosed space.

What to do when a Winter Storm Warning is issued

Once a warning is in effect, the NWS advice shifts from preparing to protecting yourself:

  • Delay travel until conditions improve, as the NWS recommends for Winter Storm Warnings. For a Blizzard Warning, the agency says do not travel at all.
  • If you must drive, the NWS urges drivers to “take it slow in the snow,” let someone know your route and timetable, and avoid traveling alone. The agency says that on average more than 5,000 people are killed and more than 418,000 are injured each year in weather-related vehicle crashes.
  • Stay sheltered. Ready.gov says winter storms raise the risk of car accidents, hypothermia, frostbite, carbon monoxide poisoning and heart attacks from overexertion.
  • Keep alerts on. According to the NWS, Wireless Emergency Alerts are sent automatically to capable phones with no sign-up required.

Where to check your local alerts

Your local NWS office is the official source for watches and warnings. Enter your ZIP code or city at weather.gov to see active alerts for your exact location, or check the NWS winter warnings, watches and advisories page for the full list of products.

For the latest storm coverage, radar and alerts across the country, follow the LiveNewsWorld U.S. Weather Live center.

Is a Blizzard Warning the same as a Winter Storm Warning?

No. A Blizzard Warning is based on strong wind and very low visibility for at least three hours, according to the NWS. It can be issued even when snowfall totals are modest, because blowing snow creates the danger.

The bottom line

A Winter Storm Watch is a heads-up that a significant storm is possible, usually a day or two out. A Winter Storm Warning means the storm is here or about to arrive, and it is time to stay off the roads. Because each NWS office sets its own thresholds, the safest approach is to treat any local warning seriously, use the watch period to stock up and plan, and check official NWS updates as the storm approaches.

Sources