GrowZone guide

How frost dates work

Frost dates are probability estimates, not guarantees. Here is how to use them without over-trusting them.

Reviewed by GrowZone Editorial, data notes from NOAA climate normals · Last updated June 28, 2026

1. A last-frost date is usually a risk threshold, not the last cold night nature will ever send

A last-frost date is usually a risk threshold, not the last cold night nature will ever send.

2. Use it with plant tolerance: tomatoes need warmer soil than spinach, so the same ZIP can have several correct planting windows

Use it with plant tolerance: tomatoes need warmer soil than spinach, so the same ZIP can have several correct planting windows.

3. Microclimates matter

Microclimates matter. A low backyard, balcony, or windy hill can run colder than the nearest station.