About US Grow Zones
US Grow Zones helps U.S. home gardeners answer two questions: what will survive my winter? and when should I plant? Every number on the site comes from public scientific data, and every frost date names the weather station it came from.
What you'll find
- A ZIP code lookup for the 2023 USDA plant hardiness zones (all 40,502 ZIP codes in the PRISM/OSU listings).
- Frost dates, frost-probability charts and a 20-crop planting calendar for 512 cities in all 50 states and DC.
- Pages for all 26 half-zones and 20 crops, and in-depth guides with cited sources.
Who runs it
US Grow Zones is a small independent website. It is not written by a government agency, a university or a Cooperative Extension service, and it does not claim credentials it doesn't have. Instead of opinions, the site's value is in carefully processed public data: we explain how every figure is computed on the methodology page, and the guides link to the original agency and university sources so you can check them.
How pages are made
City, zone and crop pages — including their question-and-answer sections — are generated by software from the datasets below, so each answer reflects that page's own numbers (for example a city's station, frost probabilities, season length and 2012-to-2023 zone change). The guides are written by hand and cite their sources. Nothing on the site is paid placement.
Data sources and versions
| Data | Source | Version / period |
|---|---|---|
| Hardiness zones by ZIP code | PRISM Group, Oregon State University | 2023 USDA PHZM ZIP listings (1991–2020); 2012 listings (1976–2005) for comparisons |
| Frost & freeze probabilities, growing season | NOAA NCEI U.S. Climate Normals | 1991–2020 annual/seasonal normals (released 2021, v1.0.1 2023) |
| City population | U.S. Census Bureau | Vintage 2024 subcounty population estimates |
| City coordinates, ZIP code (ZCTA) centers | U.S. Census Gazetteer files | 2024 |
| ZIP code–city overlap | U.S. Census Bureau ZCTA–place relationship file | 2020 |
| City elevation | USGS Elevation Point Query Service | 3DEP |
Datasets were downloaded and processed in October 2026. NOAA updates its normals every ten years and USDA updates the zone map irregularly; when either changes, we will rebuild every page. Each page shows the date its content last changed.
Independence
This site is not affiliated with or endorsed by the USDA, Oregon State University, NOAA, the Census Bureau or any Cooperative Extension service. The official USDA map is at planthardiness.ars.usda.gov. Maps on this site are our own renderings of ZIP code data, not the official map.
Advertising
The site is free and supported by advertising. Ads never change the data, and pages are not written around advertisers.
Corrections
If a zone, a frost date or a station looks wrong for your area, please contact us with the page URL and your ZIP code. Errors are corrected and the page's “last updated” date changes when they are.