Weather Stories

What do frost advisories and freeze warnings mean?

INDIANAPOLIS (WISH) — Chillier air is here for Indiana, prompting frost advisories and freeze warnings for Wednesday morning.

The purpose of these weather alerts are to help people make decisions with temperature-sensitive plants at the beginning or end of the growing season. Since we are at the beginning of the spring growing season, these alerts can be issued.

Frost advisories are typically issued when low temperatures will fall to 36 degrees or below along with favorable conditions for frost. People can protect plants by covering them up before sunset to help retain heat near the plant.

Freeze warnings are usually issued when lows are expected to 32 degrees or below. When this happens, widespread frost will kill some tender plants.

Since 1943, Indianapolis has had an average last frost on April 29. There is an old saying that is popular in many spots of the northern United States: Do not plant until after Mother’s Day,” the second Sunday of May.

For Indiana, that saying holds up pretty well considering 75% of the state’s last frosts on record have occurred by May 12, with 75% of last freezes happening by April 30.

A hard freezing warning is a step higher than a freeze warning. This type of warning is issued when low temperatures are expected to get down to 28 degrees or below. Most plants will be killed with this type of freeze during the growing season.