Last Frost Date by ZIP Code

How to find your frost dates

1. Enter your ZIP code. The tool measures from the center of your ZIP code to every NOAA weather station with frost records and starts with the closest one.
2. Choose how much risk you’ll accept. The typical setting gives the date most charts print. The cautious setting moves the spring date later and the fall date earlier, and the early setting does the opposite.
3. Choose how cold. Freeze at 32 °F is the usual meaning of a last frost date. Light frost at 36 °F matters for tender seedlings, and hard freeze at 28 °F for hardy crops such as kale and cabbage.
4. Read the station line. If that station sits much higher or lower than your ZIP code, or on the other side of a ridge or a big lake, try the second or third one.
5. Tap “Add both dates to my calendar” to download a small .ics file. Your phone or computer adds the spring and fall dates, each with a reminder a week ahead.

How the dates are worked out

Every ten years NOAA’s National Centers for Environmental Information publishes U.S. Climate Normals, 30-year summaries of weather station records. The 1991–2020 set includes frost and freeze probabilities for 7,305 stations. For each one, NOAA works out the date after which a spring night at or below a given temperature still happens in 10, 50, or 90 percent of years, and the date by which the first fall one has happened in 10, 50, or 90 percent of years.

That makes the 10 percent dates the safe ones. In spring, only 1 year in 10 has a freeze after the 10 percent date. In fall, only 1 year in 10 has one before it. Together they mark a shorter season, and at least 4 years in 5 get through it without a freeze. NOAA’s field names make this easy to read backward, so our tests check the direction against Central Park’s published values.

To pick stations, we take the ZIP code’s center point from the Census Bureau’s ZIP Code Tabulation Areas, or from GeoNames for PO box ZIP codes the Census doesn’t map, and measure the distance to every station. NOAA grades each station’s normals as standard, representative, provisional, or estimated. We prefer the first two and put a provisional or estimated station first only when it’s more than 15 miles closer. The height of your ZIP code’s center comes from USGS elevation data.

Frost, freeze, and hard freeze

The National Weather Service issues a frost advisory when lows are forecast at 33 to 36 °F on clear, calm nights, a freeze warning at 32 °F or below, and a hard freeze warning at 28 °F or below. Stations measure the air a few feet above the ground, and on still nights leaves can ice over while the shelter reads 36 °F. That’s why the 36 °F dates are worth a look for seedlings. They usually fall a week or two inside the 32 °F ones.

When frost is rare

At stations in South Florida, Hawaii, Puerto Rico, and parts of the Southern California coast, nights at 32 °F are too rare for NOAA to date. The tool says so and shows any temperature that does have dates. Where frost can come in any month, as at some high mountain stations, NOAA gives no dates either. The tool then shows how many days in a row a typical year stays above that temperature and names a nearby station with dates, if one of the three closest has them.

A worked example

Take ZIP code 10001 in Midtown Manhattan. Its center sits 32 feet above sea level. The closest station is Central Park, 2.4 miles away and about 100 feet higher. At 32 °F with the typical setting, the last spring frost comes around March 30 and the first fall frost around November 20, 235 days apart.

The table under the result shows the spread. With the cautious setting the window shrinks to April 9 through November 6. With the early setting it stretches from March 14 to December 6. So if you set out tomato plants on March 30, a freeze follows in about half of all springs.

Now switch stations. LaGuardia Airport, 6.4 miles away beside the water, averages March 26 and November 25. Teterboro Airport in New Jersey, 7.6 miles away and inland, averages April 3 and November 4. Within eight miles, the typical first fall frost moves by three weeks. If your garden is near open water, LaGuardia’s numbers may fit better, and if it sits on low inland ground, Teterboro’s may.

Tips for working with frost dates

• Plan tender plants around the cautious date, then watch the 10-day forecast. A frost advisory is your cue to cover plants for the night.
• Cover rather than give up. One cold night often comes before weeks of mild weather, and a sheet or frost cloth over the plants can carry them through it.
• Mind the low spots. Cold air drains downhill and pools in hollows, so the bottom of a slope can frost while the top stays clear.
• Keep a simple record of the first and last frost in your own yard. After a few years you’ll know how your garden compares with the station.
• Check again after the next update. NOAA recalculates the normals every ten years.