What Is a Blizzard? — In Plain Words

General information only.

Short answer

When the National Weather Service calls it a blizzard, it means a Blizzard Warning. That warning is about two things happening together: very low visibility from snow and strong wind.

It is not a warning based on how cold it is, and it is not a warning based on how much snow falls in total.

What this page covers

This page explains, in plain words, when the National Weather Service calls it a blizzard. It is based on one section of one page from the National Weather Service: the Blizzard Warning section of “Watch/Warning/Advisory Definitions,” from the Weather Service office in Baltimore/Washington.

Cross-reference, in plain text only: See also the companion guide about snow squall warnings — a snow squall is a different warning, and this page is about the blizzard warning only.

The Blizzard Warning definition

A Blizzard Warning means that the following conditions are occurring or expected within the next 12 to 18 hours.

Both of these conditions must be met:

1. Snow and/or blowing snow reducing visibility to 1/4 mile or less for 3 hours or longer
2. Sustained winds of 35 mph or greater or frequent gusts to 35 mph or greater.

The word AND stands between the two conditions in the definition. One condition on its own is not enough. The visibility condition and the wind condition must happen together.

No temperature requirement

There is no temperature requirement that must be met to achieve blizzard conditions.

That sentence is part of the Blizzard Warning definition itself. Cold alone does not make a blizzard, and a blizzard does not have to reach any set temperature to count as one.

What the definition does not use

Note: How much snow falls in total is not one of the two blizzard conditions. The definition above lists only the visibility condition and the wind condition, so the total amount of snowfall does not decide whether the warning is a Blizzard Warning.

The first condition is worded as snow and/or blowing snow. That wording means the low visibility can come from blowing snow, and not only from snow that is falling at the time, as long as the visibility and wind conditions above are both met.

So the test in the definition is visibility plus wind, within the next 12 to 18 hours, with no temperature requirement.

General information only.