Watch vs warning › Ice storm warning
National Weather Service alert guide
Ice storm warning
An ice storm warning is usually issued for ice accumulation of around a quarter inch or more. That much ice makes travel dangerous or impossible and brings down power lines and tree branches.
Ice is the winter hazard that takes the power out for days. Plan for cold and dark, not just for a bad drive.
What the National Weather Service says
Ice Storm Warning
Usually issued for ice accumulation of around 1/4 inch or more.
- Issued by
- Your local National Weather Service forecast office.
- How long it lasts
- The expiration time is written in the alert. Check it there.
Winter Storm Watch
Issued when conditions are favorable for a significant winter storm event (heavy sleet, heavy snow, ice storm, heavy snow and blowing snow or a combination of events).
- Issued by
- Your local National Weather Service forecast office.
- How long it lasts
- A Winter Storm Watch is issued when there is the potential for significant and hazardous winter weather within 48 hours.
Winter Weather Advisory
Issued when snow, blowing snow, ice, sleet, or a combination of these wintry elements is expected but conditions should not be hazardous enough to meet warning criteria.
- Issued by
- Your local National Weather Service forecast office.
The National Weather Service winter safety page defines the Ice Storm Warning. It does not define a separate ice storm watch. Ahead of the event, the alert you are most likely to see first is a Winter Storm Watch, whose definition includes ice storms.
A small amount of freezing rain is enough to make a road undrivable long before it reaches ice storm warning level.
The 48 hour figure for a watch comes from the National Weather Service office in Baltimore and Washington, cited at the end of this page.
What to do
If a winter storm watch is issued and icing is possible
- Cancel or move any travel you can.
- Charge every phone and battery pack now, while you still have power.
- Get out flashlights and check your weather radio batteries.
- Fill your gas tank. Gas pumps do not work without power.
- Get water, food that needs no cooking, and any medicine you need.
- Work out where you would go if your house lost heat for two or three days.
- Park away from large trees and power lines if you can.
If an ice storm warning is issued
- Travel is strongly discouraged. Stay off the road.
- Stay inside and away from windows near large trees. Limbs come down under the weight of ice.
- Treat every downed power line as live. Stay far away and call your utility or 911.
- Never run a generator, a grill, or a camp stove inside a house, a basement, or a garage. Keep the generator outside and far from windows.
- Do not heat a house with a gas oven.
- When using heat from a fire place, wood stove, or space heater, use fire safeguards and properly ventilate.
- Close off rooms you do not need and dress in layers to hold heat.
- Check on older neighbors and anyone who depends on powered medical equipment.
Common questions
How much ice causes an ice storm warning?
An Ice Storm Warning is usually issued for ice accumulation of around a quarter inch or more. That amount makes travel dangerous or impossible and is enough to snap power lines and tree branches. Less ice than that can still make roads and sidewalks undrivable and unwalkable.
Source: www.weather.gov/safety/winter-wwIs there an ice storm watch?
The National Weather Service winter safety page does not define one. Before an ice storm you will usually see a Winter Storm Watch, which is issued when conditions are favorable for a significant winter storm event, and its definition includes ice storms. Treat that watch as your signal to prepare for icing.
Source: www.weather.gov/safety/winter-wwIs an ice storm warning worse than a winter storm warning?
They cover different hazards and both mean stay off the road. An ice storm warning is specifically about ice accumulation, usually around a quarter inch or more, which is the amount that brings down power lines and tree branches. For power outages lasting days, ice is usually the worse of the two.
Source: www.weather.gov/safety/winter-wwHow an ice storm warning reaches you
Ice Storm Warnings are not on the National Weather Service list of alerts sent to cell phones as Wireless Emergency Alerts. Do not expect your phone to buzz for one.
This matters more for ice than for most hazards, because an ice storm is likely to take out the power and the cell service you would otherwise use to follow it.
Source: www.weather.gov/wrn/weaHow an ice storm warning reaches you when the power is out
NOAA Weather Radio All Hazards broadcasts official Weather Service warnings, watches, forecasts and other hazard information 24 hours a day, 7 days a week, directly from the nearest National Weather Service office.
A battery powered weather radio is the right tool for an ice storm specifically, because it does not need power, internet, or a cell tower.
Source: www.weather.gov/nwr