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GROWERBUDDY
Growing zones and frost dates

What Zone Am I In? Find Your Last Frost Date

A ZIP code is enough to get the two answers that decide a season: your USDA plant hardiness zone, read at your own coordinates, and the average last spring and first fall freeze from the closest weather station with a long record. Two gardens in the same zone can still sit three weeks apart.

Last updated October 14, 2026 · 5,255 stations

Try

ZIP codes and city names both work. A state name returns the state's range.

Reading the numbers

What the dates do and do not promise

The 50% date is a coin flip

Half of the recorded years had a freeze after this date, and half had their last freeze before it. Planting to it means planting into a real risk in the years that run cold.

The safer date is the one to plant against

It comes from the coldest tenth of years in the record, so it holds in nine winters out of ten. It costs one to three weeks of season, which is cheaper than a lost round of transplants.

Hard freeze is a different number

A light freeze at 32°F nips the surface and leaves most plants alive. At 28°F the damage reaches fruit blossoms and tender stems, which is why the dataset carries both thresholds. In the warmest zones 28°F is rare enough that a station never accumulates twenty such winters, and that date is left out rather than averaged from a handful of cold years.

The pattern

Where the first and last freeze land

Both maps plot the same 5,255 stations and colour each one by the date it reports: the spring map for when the season opens, the autumn map for when it closes. The colour axis runs along each season rather than between them, so tan is early and dark green is late on both.

United States map of 5,255 NOAA weather stations coloured by their average last spring freeze: tan across the South and the warm coasts, dark green across the northern states and the Rockies.
Average last spring freeze. Spring reads north to south: the last freeze lands in January along the Gulf and in the low deserts, and holds until May or June through the northern tier and the mountain valleys.
United States map of 5,255 NOAA weather stations coloured by their average first fall freeze: dark green along the Gulf coast, Florida and the desert southwest, rust and tan across the northern states.
Average first fall freeze. Autumn is the same gradient reversed: the northern states freeze from early September, while the Gulf coast, Florida and the desert southwest wait until November or December.
State by state

Frost dates across the states

Every station in a state gives a range rather than a date: elevation, distance from the coast, and latitude move the first and last freeze by weeks. The ranges below come from the same station records the lookup uses.

Frost dates across the states
StateZonesLast spring freezeFirst fall freezeStations
Alabama7b – 9bJan 30 – Apr 16Oct 21 – Dec 1883
Arizona5b – 10aJan 13 – Jun 24Aug 31 – Dec 30135
Arkansas7a – 8bMar 10 – Apr 15Oct 17 – Nov 23100
California6a – 10bJan 4 – Jun 16Sep 5 – Dec 28281
Colorado3b – 7aApr 18 – Jun 22Aug 28 – Oct 22161
Connecticut6a, 6b, 7aApr 6 – May 11Oct 5 – Nov 720
Delaware7b, 8aMar 24 – Apr 12Oct 27 – Nov 126
Florida8b – 10bJan 10 – Mar 22Nov 11 – Dec 3099
Georgia7a – 9bFeb 12 – Apr 27Oct 17 – Dec 1198
Idaho4b – 7bMar 25 – Jun 22Aug 27 – Nov 4108
Illinois5a – 7bMar 25 – May 3Oct 2 – Nov 11130
Indiana5b – 7bMar 30 – Apr 30Oct 5 – Nov 893
Iowa4b – 6aApr 6 – May 12Sep 23 – Oct 27133
Kansas5b – 7aApr 1 – May 12Oct 3 – Nov 3150
Kentucky6b, 7a, 7bMar 30 – Apr 28Oct 4 – Nov 260
Louisiana8b – 10aJan 17 – Mar 26Nov 2 – Dec 2973
Maine3b – 6aApr 21 – Jun 8Sep 5 – Oct 2866
Maryland6a – 8aMar 20 – May 12Oct 7 – Nov 2633
Massachusetts5b – 7bApr 3 – May 14Sep 26 – Nov 1752
Michigan4a – 7aApr 14 – Jun 5Sep 7 – Nov 3135
Minnesota3a – 5aApr 20 – May 31Sep 10 – Oct 21138
Mississippi7b – 9aFeb 11 – Apr 12Oct 22 – Dec 580
Missouri5b – 7bMar 26 – Apr 28Oct 9 – Nov 6136
Montana3b – 6bMay 1 – Jun 18Aug 29 – Oct 15182
Nebraska4b – 6aApr 11 – Jun 5Sep 6 – Oct 22138
Nevada5a – 10aJan 20 – Jun 18Sep 1 – Dec 1284
New Hampshire4a – 6aApr 19 – Jun 3Sep 15 – Oct 1738
New Jersey6b – 8aMar 23 – May 3Oct 11 – Nov 2038
New Mexico5a – 8bMar 15 – Jun 20Sep 8 – Nov 14146
New York4a – 7bMar 27 – Jun 4Sep 9 – Nov 22126
North Carolina6a – 9aMar 4 – May 17Oct 4 – Dec 11149
North Dakota3b, 4a, 4bMay 2 – May 24Sep 16 – Oct 8101
Ohio5b – 7aApr 5 – May 17Oct 2 – Nov 15109
Oklahoma6b – 8aMar 20 – Apr 25Oct 12 – Nov 1987
Oregon5b – 9bFeb 25 – Jun 18Aug 30 – Nov 30135
Pennsylvania5b – 7bMar 27 – May 29Sep 20 – Nov 26121
Rhode Island6b, 7aApr 10 – May 6Oct 9 – Nov 49
South Carolina7b – 9aFeb 8 – Apr 13Oct 22 – Dec 1871
South Dakota4a – 5bApr 25 – Jun 5Sep 6 – Oct 10123
Tennessee6a – 8aMar 14 – May 20Sep 30 – Nov 15126
Texas6b – 10aJan 13 – Apr 29Oct 13 – Dec 24377
Utah4b – 8bMar 2 – Jun 20Aug 19 – Nov 22134
Vermont4a – 5bApr 27 – Jun 1Sep 10 – Oct 1833
Virginia6a – 8bMar 12 – May 15Sep 30 – Nov 26100
Washington5b – 9aFeb 24 – Jun 10Sep 7 – Nov 30130
West Virginia5b – 7aApr 5 – May 20Sep 22 – Nov 383
Wisconsin4a – 6aApr 13 – May 27Sep 14 – Oct 24151
Wyoming3b – 5bMay 6 – Jun 26Aug 12 – Oct 594

Zones are the USDA 2023 plant hardiness zones at those stations, and the frost dates are the 50% dates averaged across the stations in the state. Station records generated 2026-10-14.

Where the numbers come from

One method, stated out loud

Thirty winters of daily minimums

For each station, the last spring freeze is the latest date in the first half of the year with a daily minimum at or below freezing, taken across the 1991-2020 record. The first fall freeze is the earliest such date in the second half. A station stays in the dataset only with at least twenty usable winters behind it.

Two probabilities from one record

Sorting every year's last spring freeze gives the distribution the two dates come from: the middle year is the 50% date, and the ninth-coldest year out of ten is the safer one. The fall dates are read the same way from the other end of the year.

Zones answer a different question

A USDA zone is the average annual extreme minimum temperature over the same thirty years. It tells you which perennials survive your coldest night, and it says nothing about when your last spring freeze arrives: the same zone covers coastal and high-desert gardens with months between their planting dates.

The nearest station is not your garden

A station can sit twenty miles away and a thousand feet lower, and cold air pools in valleys that the station's ground misses. A hilltop garden, a walled courtyard, and a lake shore all run warmer than the surrounding countryside. When the answer matters, put a thermometer at the height of the plants and compare it with the nearest station for a season.

Your frost date is the floor, not the plan

Once you know the window, the next question is what is ready to go in this week. The planting calendar reads live soil temperature and the forecast for your location and answers that one.

Open the planting calendar
FAQ

Questions the numbers raise once you have them

What a zone decides, what a frost date does not promise, and why two sites can print different dates for the same ZIP code.

What growing zone am I in?

The lookup returns the zone for the nearest station with a long record. USDA assigns zones from the average coldest night each winter, so zone 6a means the annual low has averaged between -10°F and -5°F over thirty years. Use the zone to judge whether a perennial survives your winters, and the frost dates to decide when an annual goes outside.

How do I find my last frost date?

It comes from daily low temperatures at one station rather than from a zone. Half of the years in that station's record froze after the 50% date, and half were finished before it. The safer date is the one from the coldest tenth of years, which is what to plant against when a late freeze would cost you the crop.

Why does another site give a different frost date?

Three things move it. The probability threshold differs, so a 32°F date and a 36°F date can be a fortnight apart. The station differs, and a station in a river valley reads colder than one on the ridge above it. The years differ, because a 1981-2010 average and a 1991-2020 average are not the same climate. Ask which station and which years before treating a date as wrong.

Is frost possible at 40 degrees?

On the ground, yes. Official temperatures are measured about five feet above the soil, and on a clear, calm night the surface a few inches down is several degrees colder than the air at that height. A forecast low of 36-38°F with no wind is enough for frost on a lawn while the station reads above freezing. Wind and cloud are what stop it.

Does my last frost date tell me when to plant?

It tells you when the odds of a freeze drop, and that is the earliest a tender crop should go out. Soil temperature decides the rest: tomatoes and peppers want the soil above about 60°F, and a cold, wet week after the average date sets transplants back more than a week of waiting does. Check the forecast for the days after planting rather than the date alone.

Which places does the lookup cover?

The 48 contiguous states, from about 800 stations with long records. Alaska, Hawaii, and the territories are not in this dataset yet, so a ZIP code there will return the nearest mainland match rather than the right one.

Sources behind the numbers

Zones come from the USDA plant hardiness map and the station records from NOAA; the freeze method is described above the answers.