Last Frost Date By Zip Code
Match a ZIP to nearby NOAA 1991–2020 32°F probability dates, with the station, distance and USDA zone kept explicit. Inputs stay in your browser.
CalcSpan matches the ZIP locally to a nearby NOAA 1991–2020 climate-normal station, then applies the selected probability threshold. USDA hardiness zone is shown separately and never used to invent frost dates.
Calculate to load the current reference data before saving.
Context matters.
- A ZIP is a search aid, not a weather station. If the automatic station differs materially in elevation, coast exposure or terrain, use the NOAA station override.
- USDA hardiness zones summarize annual extreme minimum temperature and are not frost dates.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Match a ZIP to nearby NOAA 1991–2020 32°F probability dates, with the station, distance and USDA zone kept explicit. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses U.S. ZIP Code, Planning year, Freeze-risk threshold and NOAA station ID override (optional) supplied in the form.
- Apply the scope. It applies the United States — NOAA 1991–2020 station normals, Census ZCTA matching and USDA 2023 hardiness-zone reference reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
CalcSpan matches the ZIP locally to a nearby NOAA 1991–2020 climate-normal station, then applies the selected probability threshold. USDA hardiness zone is shown separately and never used to invent frost dates.
- NOAA climate stationLoaded after Calculate span
Calculation purpose: Match a ZIP to nearby NOAA 1991–2020 32°F probability dates, with the station, distance and USDA zone kept explicit. This is a general planning reference; local conditions, product instructions or personal records can override the estimate.
Numeric inputs are constrained by the field limits and the result keeps the entered units visible. Zero, minimum, maximum and non-finite values are treated as input boundaries.
Rule set 2.0.0 · Last reviewed 2026-08-28 · Next review due 2027-02-28. The source panel below contains the linked evidence.
What to know before using the result.
Is a USDA hardiness zone the same as a frost date?
No. USDA zones describe annual extreme minimum temperature for perennial-plant cold tolerance. CalcSpan obtains 32°F probability dates from NOAA climate normals and shows the zone only as a separate reference.
What does the 10% freeze-risk threshold mean?
At the selected NOAA station, there is a 10% modeled chance the last spring 32°F event occurs later than the shown spring date, and a 10% chance the first fall event occurs earlier than the shown fall date.
Why does the calculator show a NOAA station and distance?
Frost normals are calculated at weather stations, not ZIP codes. Distance, elevation, coast exposure, slope and cold-air drainage help you judge whether the automatically matched station represents your site.