WeatherWeather Science


What is the difference between a frost advisory, freeze warning, and hard freeze warning?

Frost on flowers
Posted at 2:43 PM, Oct 13, 2022
and last updated 2022-10-13 18:53:16-04

On Thursday morning, southern Colorado saw a frost advisory, freeze warning, and hard freeze warning all in effect at the same time.

So what is the difference between these three different weather alerts and how should you prepare for each one?

Frost Advisory

A frost advisory is issued by the National Weather Service when frost development is expected for 2 hours or longer in an area. Frost, AKA "frozen dew", can form on roofs, grass, trees, cars, etc. when air temperatures are as high as 37°. This depends on the wind, humidity, cloud cover, etc.

A frost can kill sensitive plants, but the growing season can continue after a frost occurs. Cover sensitive plants and bring in potted plants during a frost advisory.

Freeze Warning

A freeze warning is issued when the first freeze of the season is expected, where temperatures will drop to 32° or lower for 2 hours or longer.

A true freeze can kill crops and end the growing season for many plants. Hardy plants can survive in the low 30s. Pipes are usually okay at this temperature.

Hard Freeze Warning

A hard freeze warning is issued when temperatures drop below 28° for 2 hours or longer.

A hard freeze is usually the final warning to winterize your home and harvest your garden. Outdoor pipes or sprinkler systems can be damaged if not protected or drained. The growing season will end at these temperatures.

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