Frost dates
Your frost dates come from a weather station, not a zone map.
A hardiness zone is the coldest night of winter. It says nothing about when spring's last freeze lands — two gardens in one zone can be three weeks apart. These are the dates NOAA measured: 1991–2020 freeze normals from 7,277 stations, matched to 33,679 US ZIP codes.
Largest cities
- New York, NYApr 1 → Nov 19
- Los Angeles, CAfrost rare
- Chicago, ILApr 10 → Nov 5
- Houston, TXFeb 2 → Dec 25
- Phoenix, AZJan 8 → Dec 25
- Philadelphia, PAMar 30 → Nov 17
- San Antonio, TXFeb 25 → Nov 28
- San Diego, CAfrost rare
- Dallas, TXMar 2 → Nov 29
- Jacksonville, FLFeb 1 → Jan 5
- Fort Worth, TXMar 5 → Nov 24
- San Jose, CAJan 2 → Dec 25
- Austin, TXFeb 20 → Dec 3
- Charlotte, NCMar 30 → Nov 3
- Columbus, OHApr 20 → Oct 24
- Indianapolis, INApr 20 → Oct 21
- Seattle, WAMar 13 → Nov 17
- Denver, COMay 4 → Oct 8
- Oklahoma City, OKApr 4 → Nov 2
- Nashville, TNApr 1 → Oct 31
- Washington, DCMar 29 → Nov 8
- El Paso, TXMar 2 → Nov 20
- Las Vegas, NVJan 24 → Dec 10
- Boston, MAApr 4 → Nov 9
By state
How to read a frost date
NOAA doesn't publish one frost date per place. It publishes odds. For the last spring freeze (32 °F), each station gets three dates: the one with a 90% chance of another freeze still to come, the median (a coin flip), and the one with only a 10% chance. The first fall freeze gets the same treatment in reverse.
Most "last frost date" charts print the median and stop. That's a date you'll lose transplants on half the time. Every city page here shows all three. The planting calendars run on the median and then apply each crop's own offset: onions and cilantro go out weeks before it, tomatoes and peppers one to two weeks after. If you can't throw a cover over tender transplants on a cold night, move them to the 1-in-10 date instead.
Each ZIP maps to the nearest station with a complete freeze record, up to 60 km away; cities use the station for their most central ZIP, so a city page and a Plan Builder ZIP lookup always agree. Elevation matters: frost pools in valleys, so treat a station on a hill as a few days optimistic for the creek bottom below it. More in frost dates and days to maturity.
Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal, by station); U.S. Census Bureau 2024 Gazetteer and Vintage 2024 population estimates; USDA 2023 Plant Hardiness Zone Map ZIP tables (PRISM Climate Group, Oregon State University).