Blizzard
A blizzard is a storm with sustained winds or frequent gusts of 35 mph or more and falling or blowing snow that frequently reduces visibility to below a quarter mile, lasting 3 hours or longer. The National Weather Service definition has no snowfall or temperature requirement: wind and visibility make a blizzard.
Why It Matters
A blizzard is defined by what makes it dangerous: strong wind and near-zero visibility. Blowing snow can make travel impossible whether or not much new snow is falling, which is why the definition ignores snowfall totals.
National Weather Service Blizzard Criteria
| Factor | Requirement |
|---|---|
| Wind | Sustained winds or frequent gusts of 35 mph or more |
| Visibility | Frequently below 1/4 mile in falling and/or blowing snow |
| Duration | 3 hours or longer |
| Snowfall amount | No requirement |
| Temperature | No requirement |
Common Misconceptions
- A heavy snowstorm is not automatically a blizzard. Two feet of snow with light wind does not qualify.
- A blizzard does not need falling snow. Strong wind lifting snow already on the ground can meet the criteria, which is called a ground blizzard.
- A blizzard does not need extreme cold. There is no temperature threshold in the definition.
Frequently Asked Questions
How much snow does it take to be a blizzard?
None in particular. The definition has no snowfall requirement. A blizzard needs sustained winds or frequent gusts of 35 mph or more and visibility frequently below a quarter mile in falling or blowing snow, for 3 hours or longer.
What is a ground blizzard?
A blizzard caused by wind blowing snow that has already fallen, with little or no new snow. The criteria count blowing snow as well as falling snow, so the wind and visibility thresholds can be met without a snowstorm overhead.
What is a Blizzard Warning?
A National Weather Service warning issued when blizzard conditions are expected: sustained or frequent winds of 35 mph or higher with falling or blowing snow frequently cutting visibility to a quarter mile or less, for at least 3 hours.
Related Terms
Snow Squall
An intense, short-lived burst of heavy snow accompanied by strong winds and often causing a sudden drop in visibility to near zero. Snow squalls can create extremely dangerous driving conditions despite lasting only 30-60 minutes.
Nor'easter
A storm along the East Coast with winds blowing from the northeast. Nor'easters can bring heavy snow, rain, and coastal flooding, especially from Virginia to New England. The most powerful nor'easters rival hurricanes in intensity.
Bomb Cyclone
A bomb cyclone is a midlatitude storm that intensifies rapidly through a process called bombogenesis: its central pressure falls by at least 24 millibars in 24 hours, measured at 60° latitude. The threshold shrinks toward the equator, to about 17.8 millibars at the latitude of New York City.
Lake Effect Snow
Intense, localized snowfall produced when cold air moves across relatively warm lake water, picking up moisture and heat. Lake effect snow can produce snowfall rates of 2-4 inches per hour and create dramatic differences in accumulation over short distances.
Wind Chill
Wind chill is how cold the air feels on exposed skin once wind is taken into account. Wind strips heat from the body faster than still air does, so the wind chill temperature is lower than the air temperature. At 0°F with a 15 mph wind, the wind chill is -19°F, and exposed skin can freeze in 30 minutes.
Alberta Clipper
A fast-moving low-pressure system that originates near Alberta, Canada, and tracks southeast across the northern United States. Clippers typically bring light snow (1-4 inches) followed by bitter cold and gusty winds.
Visibility
The horizontal distance at which objects can be seen and identified. U.S. aviation reports express prevailing visibility in statute miles. Below 3 statute miles falls in the IFR or LIFR weather category, but legal visual-flight minimums vary with airspace, altitude, and day or night under 14 CFR 91.155.
Blizzard: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
In-depth guide
Winter Storm Watch vs Warning vs Winter Weather Advisory (Plus Blizzard, Ice Storm, and Snow Squall Warnings)
What a Winter Storm Watch, Winter Storm Warning, and Winter Weather Advisory mean, how many inches of snow trigger a warning where you live, and how Blizzard, Ice Storm, Snow Squall, and Extreme Cold Warnings differ.
Weather Education
Watch vs Warning vs Advisory vs Outlook: NWS Weather Alerts Explained
Learn the difference between a weather watch, warning, advisory, and outlook, what a Special Weather Statement means, and when to prepare versus take immediate action.
Weather Education
Frost Advisory vs Freeze Warning vs Hard Freeze: What Each One Means
A Frost Advisory usually means lows of 33 to 36°F, a Freeze Warning 32°F or colder, and a hard freeze about 28°F or colder. Learn why frost forms above freezing, why the alerts stop in late fall, and what to protect at each level.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Tool
Wind Chill Calculator
Estimate cold-weather exposure risk from temperature and wind speed.
Seasonal Hub
Winter Weather Guide
Find practical explainers on snow, freezing rain, wind chill, and winter travel risk.
Tool
Snow-to-Liquid Ratio Calculator
Estimate snowfall from liquid equivalent and snow-to-liquid ratio.
Tool
Wind Speed Converter
Convert between mph, km/h, knots, and m/s for wind reports and forecasts.
Sources
Explore Other Terms
Ceiling
The height above ground of the lowest broken or overcast cloud layer, or vertical visibility into an obscuration. Scattered clouds do not form a ceiling. A ceiling below 1,000 feet falls in the IFR or LIFR weather category; legal flight and approach requirements depend on airspace, visibility, regulations, equipment, and pilot qualifications.
Cyclone
A rotating low-pressure weather system. Tropical cyclone terminology and intensity categories vary by region: in Australia, a tropical cyclone has maximum sustained winds of at least 34 knots (63 km/h, about 39 mph), averaged over ten minutes. The term does not universally require hurricane-force winds of 74 mph.
Small Craft Advisory
A Small Craft Advisory is a National Weather Service alert for winds or seas that are hazardous to small boats in coastal and Great Lakes waters. The wind and sea thresholds are set separately for each geographic area. There is no precise definition of a small craft: any vessel that the conditions could affect counts.
Red Flag Warning
A Red Flag Warning is a National Weather Service alert that weather conditions could cause extreme fire behavior. It is issued when those conditions are occurring or expected within 24 hours. Typical criteria combine dry fuels with sustained winds of 15 mph or more and relative humidity of 25% or less, and exact thresholds vary by state and local office.
El Niño and La Niña
El Niño and La Niña are the warm and cool phases of a recurring climate pattern in the tropical Pacific called the El Niño-Southern Oscillation (ENSO). During El Niño, the trade winds weaken and the central and eastern tropical Pacific runs warmer than average. During La Niña, the trade winds strengthen and the same waters run cooler. Both shift weather patterns worldwide.
Kp Index
The Kp index is a 0 to 9 scale of global geomagnetic activity, reported in 3-hour intervals from ground-based magnetometers. A Kp of 5 or higher indicates a geomagnetic storm, and the values map onto NOAA's G-scale from G1 (Kp 5) to G5 (Kp 9). The higher the Kp, the farther from the poles the aurora can be seen.
Browse by Category
In the WeatherAI App
WeatherAI displays official NWS alerts, which include Blizzard Warnings, and its severe weather tools include WPC winter-weather guidance.
Availability, coverage, update frequency, and alert delivery vary by data source, region, subscription plan, device permissions, and service conditions. WeatherAI supplements official sources and is not an emergency notification service. For life-safety decisions, rely on your national weather service, local emergency management, and official warning channels.