Frost dates: when to plant
How to use your last and first frost dates to plan the garden
What frost dates are
Your average last spring frost and first fall frost come from decades of local weather records. In the US they're based on 30 years of climate data. The frost-free period between them is your season for tender crops.
Elevation, nearby water and towns all shift the dates, so your own garden can differ from the official numbers. Forecasters issue a frost advisory when lows of 33–36°F (1–2°C) are expected; a freeze means 32°F (0°C) or below.
Average isn't a promise
An average frost date means about a 50% chance of frost after it: in half of years, the last frost came later. That's why tender crops often go out a week or two after the average date.
Planting by frost date
Most vegetables fall into one of these groups.
- Hardy crops like peas, lettuce, spinach, radishes, onions and cabbage: as early as 2–4 weeks before the last frost.
- Tender crops like tomatoes, peppers, beans and squash: after the last frost.
- The most tender, like tomatoes, peppers, eggplant and melons: often 2 weeks or more after it.
- In summer, count back from your first fall frost to time fall crops.
Use the soil, too
Soil temperature is one of the best guides to spring planting. Warm-season crops need warm soil and daytime temperatures above about 60°F (16°C). A soil thermometer takes the guesswork out.
USDA hardiness zones measure winter cold, not frost dates. Use them to choose perennials, and check your local frost dates for planting.
If frost surprises you
Bringing pots indoors is the easiest protection. Cover garden plants overnight with sheets, blankets, towels or frost cloth, held up on stakes so the cover doesn't touch the leaves. Plastic isn't advised.
Take covers off the next day once it's above freezing. Below about 28°F (−2°C), covers stop working. Cool-season crops like spinach, kale and lettuce often survive light frosts down to about that temperature.
Related plant problems
Sources
- NOAA NCEI: When to Expect the First Fall Freeze
- Missouri Botanical Garden: Frost Injury and Ice Damage
- Iowa State University Extension: How to Protect Plants from Frost and Freeze
- Colorado State University Extension: Vegetable Planting Guide
General guidance, not a diagnosis. Written by PlantWiz in our own words from the sources above.