Planting & Harvest Dates

Frost Date Calculator

Type your US ZIP code to find your average last spring frost date, first fall frost date, USDA hardiness zone, and the length of your frost-free growing season.

How to use the frost date calculator

Type your five-digit US ZIP code into the box and press Find My Frost Dates. The calculator reads the first three digits of your ZIP, matches them to your region, and instantly shows your USDA hardiness zone, your average last spring frost, your average first fall frost, and the number of frost-free growing days in between. If your exact ZIP is not in the database, try a nearby town or a larger city in your area for a close estimate.

Why frost dates matter

Frost dates are the backbone of a planting schedule. The last spring frost tells you when it is safe to set out tender crops such as tomatoes, peppers, squash, and basil, all of which are damaged or killed by freezing temperatures. The first fall frost tells you when the season will end for those same crops. Together they define your growing window and let you count backward to decide when to start seeds indoors and forward to know which varieties can finish in time.

Understanding your USDA hardiness zone

While frost dates describe your growing season, your USDA hardiness zone describes your winter. Zones are based on the average annual minimum temperature and are split into 10-degree Fahrenheit bands, each divided into warmer “a” and cooler “b” halves. The zone is most useful for choosing perennials, shrubs, and trees that need to survive winter, while frost dates are most useful for timing annual vegetables and flowers. Use them together for a complete planting plan.

Counting back from your last frost

Many seed packets say something like “start indoors 6–8 weeks before last frost.” Once you know your last spring frost date, you can count backward to schedule indoor sowing, then transplant after the danger of frost has passed. On the other end of the season, compare a crop’s “days to maturity” with your frost-free day count to make sure it has time to ripen before the first fall frost arrives.

A few important cautions

  • These are averages: roughly half of years will see frost a little later in spring or earlier in fall.
  • Local microclimates — low spots, hilltops, cities, and lakeshores — can shift your real dates by a week or more.
  • Always check the short-term forecast before planting out tender crops, and keep row covers handy for surprise late frosts.
  • Raised beds and containers warm faster in spring but can also cool faster on clear, still nights.

Frequently Asked Questions

What is a last spring frost date?

Your last spring frost date is the average date after which freezing temperatures are unlikely in spring. It marks the rough point when it becomes safe to move tender, frost-sensitive plants like tomatoes, peppers, and basil outdoors. Because it is an average, frost can still occur a week or two later, so watch the forecast before planting.

What is a first fall frost date?

Your first fall frost date is the average date in autumn when freezing temperatures typically return. It tells you roughly how long you have before frost ends the growing season for warm-season crops, helping you decide what still has time to mature and when to harvest or protect tender plants.

How are frost dates calculated?

The dates shown here are 30-year climate normals derived from NOAA weather station records. They represent the average over three decades for each region, identified by the first three digits of your ZIP code. Averages smooth out unusual years, so your local conditions in any given season may run earlier or later.

What is a USDA hardiness zone?

A USDA plant hardiness zone is a region defined by its average annual minimum winter temperature, divided into 10-degree Fahrenheit bands (with "a" and "b" half-zones). Plant labels list a hardiness zone range to show where a plant can survive the winter. Knowing your zone helps you choose perennials, shrubs, and trees that will come back year after year.

How many frost-free days do I have?

Frost-free growing days is the average number of days between your last spring frost and first fall frost. It is the length of your reliable growing season. Compare it to the "days to maturity" on a seed packet to confirm a crop has enough time to ripen before frost returns; if it is tight, start seeds indoors early.

My ZIP code was not found. What should I do?

This calculator covers a wide range of US ZIP prefixes, but not every single one. If yours is not listed, try the ZIP code of a nearby town or a larger city in your area; frost dates change gradually across a region, so a neighboring ZIP will give you a close estimate.

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GardenCalc Editorial Team

Horticulture writers & master gardeners

Our calculators and growing guides are written and fact-checked by gardeners with hands-on experience in vegetable production, soil management, and home landscaping.