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Frost Dates by ZIP Code

Enter your ZIP for your last spring frost, first fall frost, and USDA hardiness zone — with the risk level and weather station behind every date.

What is a frost date?

A frost date is the average day your area sees its last freeze of spring or first freeze of fall, calculated from 30 years of NOAA weather station records. Gardeners use it to time when it’s safe to set out tender plants in spring and when to protect or harvest before cold hits in fall. It’s not a single fixed date — frost timing varies year to year, which is why frost dates are given as a range of risk rather than one number.

Your last frost date matters for starting seeds indoors and transplanting outside. Your first frost date matters for harvesting tender crops and planting fall cover crops, garlic, and bulbs before the ground freezes.

How risk percentage works

Each frost date above comes with a risk percentage: 10%, 50%, or 90%. These describe how likely frost is to still happen after that date, based on the historical record.

The 10% dateis later in spring (or earlier in fall) — it’s the safer, more conservative choice. Only 10% of years saw frost after this spring date, so planting tender crops after it is a low-risk bet. The 50% dateis the middle of the road: half of all years had frost after it, half didn’t. It’s the number most “average last frost” charts use. The 90% dateis the earliest, riskiest choice — 90% of years still saw frost after this date, so planting that early means you’re betting on an unusually mild year.

The same logic runs in reverse for fall: a later first-frost date (10%) is the optimistic case for squeezing out more growing season, while an earlier date (90%) is the cautious one for deciding when to harvest or cover up.

Sample frost dates by city

A few real examples from across the country, at the 50% risk level (32°F threshold). Look up your own ZIP above for the 10%/90% range and hardiness zone.

CityZoneLast spring frostFirst fall frost
Denver, CO6aMay 4Oct 8
Seattle, WA9aMar 13Nov 17
Miami, FL11aRarely/never freezesRarely/never freezes
Phoenix, AZ10aJan 5Jan 3
Duluth, MN5aMay 14Oct 12
Boston, MA7aApr 4Nov 9
Chicago, IL6bApr 10Nov 5
Atlanta, GA8aMar 25Nov 9
Portland, ME6aApr 26Oct 15
Austin, TX9aMar 10Nov 17
Minneapolis, MN5aApr 23Oct 16
Sacramento, CA9bJan 12Dec 16

Related tools and guides

FAQ

What is a frost date?

A frost date is the average day your area's last spring freeze or first fall freeze happens, based on decades of weather station data. It's a statistical average, not a guaranteed day — actual frost can come earlier or later in any given year.

Should I use the 10%, 50%, or 90% frost date?

Use the 50% date for typical planning. Use the 10% (later) date if a late frost would kill an expensive or fragile planting and you want a safer margin. Use the 90% (earlier) date only if you're willing to risk replanting for a longer season.

Why does my ZIP show a hardiness zone change since 2012?

USDA updated the Plant Hardiness Zone Map in 2023 using 1991–2020 weather data. Many areas shifted half a zone or more warmer as winter lows trended up. Your zone label may differ from what's on an old seed packet or plant tag.

Why is my station so far from my ZIP code?

Frost data comes from NOAA weather stations, and not every ZIP has one nearby. When the closest station is more than a few miles away — common in rural areas, mountains, and small towns — we show a distance and a low-confidence note so you can judge how much to trust the estimate.

Does elevation or being near water change my frost date?

Yes. Microclimates from elevation, slope, and nearby lakes or coastline can shift your actual frost date from the nearest station's by a week or more. Treat these numbers as a starting point, not a guarantee — watch your own yard's conditions too.

Curious where this data comes from? Read about the sources and how we match ZIPs to weather stations, including CSV downloads and an embeddable widget.

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