Winter storms may trigger warnings, watches and advisories. What do they all mean?

For millions of us, winter has already begun. As the wind howls, the snow flies and temperatures drop, the National Weather Service is issuing various alert levels for wintry weather.

While some may sound similar, each warning issued by local weather departments signals different winter conditions. Each office knows the area and issues alerts, warnings or advisories based on criteria that vary from office to office.

For example, the amount of snow that triggers a winter storm warning in the northern Plains is typically much higher than the amount needed to trigger a similar winter storm warning in the Southeast.

Other non-storm related warnings include freeze and freeze warnings and wind chill warnings.

Fear of hypothermia, icy roads? How to stay safe during snowstorms.

Here you can find out what the terms “winter weather warning” mean:

What is a Winter Weather Advisory?

A Advice on winter weather is issued when snow, blowing snow, ice, sleet, or a combination of these wintry elements is expected, but conditions are not expected to be dangerous enough to meet the warning criteria. Be prepared for winter driving conditions and possible travel difficulties. Be careful when driving.

Map: Weather warnings for the United States

What is a winter storm watch?

A Winter Storm Watch is issued when there is a risk of significant and dangerous winter weather within 48 hours. That doesn’t mean severe and dangerous winter weather will happen – it just means it’s possible. It is issued when dangerous winter weather such as a blizzard, heavy snow, heavy freezing rain or heavy sleet is forecast. Typically it is issued 12 to 36 hours before winter weather.

What is a Winter Storm Warning?

A Winter storm warning is issued for a significant winter weather event involving snow, ice, sleet or blowing snow, or a combination of these hazards. In some situations, traveling becomes difficult or impossible. Postpone your travel plans until conditions improve. Typically it is issued 6 to 18 hours before winter weather.

What is a blizzard warning?

A Blizzard warning informs you that snow and strong winds combine to create blinding snow (near zero visibility), deep drifts and life-threatening wind chill. Specifically, it is issued when sustained or gusty winds of 35 miles per hour or greater are expected to reduce visibility at or below a quarter mile due to falling and/or blowing snow for at least three hours.

What is a lake effect snow warning?

A Lake effect snow warning is issued when pure lake effect snow (when the snow is a direct result of lake effect snow and is not due to a synoptic storm or low pressure area) may pose a hazard or be life-threatening.

What is a snow squall warning?

A Snow squalls warning is issued when a snow squall is forecast. A snow squall is an intense but limited duration of moderate to heavy snowfall accompanied by strong, gusty winds and possibly lightning (generally moderate to heavy snow showers). Snow accumulation can be significant.

What is an Ice Storm Warning?

A Ice storm warning is issued when ice accumulation of at least 1/4 inch is expected.

This article originally appeared on USA TODAY: Warnings, watches and advisories: Winter weather warnings explained