Last Frost Date by ZIP Code — Spring & Fall Frost Dates

What the 50% and 10% dates mean

A frost date is not a promise; it is a probability. Each date above comes from 30 years of nightly low temperatures at the weather station nearest your ZIP code.

Average last frost (50%). In half of years the last spring frost came after this date, and in half it came before. This is the date most seed packets and planting guides count from.
Safe date (10%). Only 1 year in 10 had a frost after this date. It is usually two to three weeks later than the average date. If you want to plant tomatoes once and not worry, plant after this one.
Average first fall frost (50%). Half of years had their first fall frost by this date.
Early date (10%). Only 1 year in 10 had a frost before this date. Plan to have tender crops picked, or covers ready, from here on.

The year chart shows the same thing as a picture. The dark blue stretch is the frost season between the two average dates. The pale blue zones on either side are the risky weeks, when frost comes in some years and not others. The green stretch is frost-free in nine years out of ten.

How to use your frost dates

Almost every planting time is counted from these two dates. Hardy crops such as peas and spinach go in four to six weeks before the last spring frost. Tomatoes and peppers are started indoors six to ten weeks before it and planted out one to four weeks after. Fall crops count backward from the first fall frost: broccoli and cabbage go in 10 to 14 weeks before it, so they mature in cool weather.

Frost is not the only signal for warm-season crops. Beans rot and peppers sulk in cold soil even after the frosts have stopped, so we also show when your normal daily average temperature reaches 60°F. You don’t need to do the arithmetic: the planting calendar turns these dates into sowing and planting windows for every crop, and the seed starting calculator tells you when to start each seed indoors.

Where the numbers come from

The dates come from the NOAA U.S. Climate Normals for 1991–2020, the official 30-year averages published by the National Centers for Environmental Information. NOAA calculates the probability of the first and last 32°F night for each station. We match your ZIP code to the nearest of 7,305 stations with those figures, measured from the center of the ZIP code area, and show you the station name and how far away it is.

If your ZIP code is a PO box or business ZIP with no map area of its own, we use the nearest ZIP code that has one and tell you which. If the station has no usable frost dates, we explain why instead of showing a broken chart.

Why your garden may differ

A station a few miles away is a good guide, not a guarantee. Gardens can be a week or two off in either direction:

Elevation. Air cools by roughly 3.5°F for every 1,000 feet you climb. In the mountains, a station in the valley town and a garden up the hill can have very different seasons.
Low spots. On clear, still nights cold air drains downhill and pools in hollows and valley floors. A garden at the bottom of a slope can get frost when the slope above stays clear.
Coasts and big lakes. Water warms and cools slowly, so places near it usually have later fall frosts and a longer season than places a few miles inland.
Cities. Pavement and buildings hold heat overnight. A garden in town often frosts later than a station at a rural airport.
Distance. If the station is more than about 25 miles away, or across a ridge, check a neighboring ZIP code or ask local gardeners.

Keep notes for a few years. If your garden reliably frosts a week after the station, shift every date a week.

Protecting plants from a late or early frost

Watch the forecast in the risky weeks. Clear skies, no wind and a forecast low in the mid-30s are the classic frost recipe.
Cover plants in the evening with frost cloth, old sheets or buckets, reaching to the ground to trap the soil’s warmth. Take covers off in the morning. Plastic touching the leaves gives little protection.
Water dry soil during the day before a frost. Moist soil holds and releases more heat than dry soil.
Bring containers in or group them against a south-facing wall.
Harvest first in fall: pick tomatoes, peppers, beans and basil before the first frost night. Kale, Brussels sprouts and other hardy crops can stay; light frosts sweeten them.

Frequently asked questions

What is the last frost date?

The average last frost date is the day in spring after which, in half of years, there are no more nights at 32°F or colder. It is the date most planting guides count from: “start seeds 6 weeks before the last frost” means six weeks before this date.

Is it safe to plant tomatoes after the last frost date?

Not quite. On the average date there is still a 50% chance of a later frost. For tender crops, wait for the 10% “safe” date, or plant around the average date with row cover ready. Tomatoes also stall in cold soil, so many gardeners wait until the daily average reaches about 60°F.

What is the difference between a frost and a freeze?

Weather services usually call air temperatures at or below 32°F a freeze. Frost is the ice crystals that form on surfaces, and on clear, still nights it can form on plants even when a thermometer five feet up reads a few degrees above freezing. Frost dates in climate records are based on the 32°F air temperature.

Why is my frost date different from my neighbor’s or a website’s?

Sources use different stations, different years and different probabilities. We use the nearest of 7,305 NOAA stations and the 1991–2020 normals, the latest official set. Sites using older normals or a 30% or 10% date can differ by a week or two. Your own yard can also be colder or warmer than the station.

How is the growing season calculated?

The average growing season is the number of days between the average last spring frost and the average first fall frost. The “9 years out of 10” figure runs from the 10% spring date to the 10% fall date, so it is the frost-free stretch you can count on in most years.

Are frost dates the same as hardiness zones?

No. A hardiness zone describes the coldest winter night, which tells you which perennials survive. Frost dates describe when the frost season starts and ends, which is what decides planting times. Two places in the same zone can have last frosts weeks apart.

What if my ZIP code shows no frost dates?

Either frost is too rare for NOAA to calculate dates, as in South Florida, Hawaii and parts of coastal California, or the station is so cold that a freeze can come in any month. A third case is a PO box ZIP with no map area; for those we use the nearest ZIP that has weather data and say so.

Frost dates by ZIP code