About the data
Planting Zone Map shows, for each of 40,483 U.S. ZIP codes, the 2023 USDA hardiness zone, the 2012 zone, the usual frost dates and a planting calendar. Everything comes from public datasets; nothing is estimated by hand.
Hardiness zones
The zones are the 2023 USDA Plant Hardiness Zone Map data, produced for the USDA Agricultural Research Service by the PRISM Group at Oregon State University. A zone is the average of each year's coldest night (annual extreme minimum temperature) over 1991–2020, in 10 °F zones split into 5 °F halves. We use PRISM's own ZIP-code table for the zone of each ZIP code and their 800 m grid for the map. The 2012 zones come from the same group's 2012 ZIP table (1976–2005 data).
We recolor and reproject the grid for the web map, so this is not the official USDA map; the official one is at planthardiness.ars.usda.gov. The zone values themselves are unchanged.
Frost dates
Frost dates are NOAA NCEI U.S. Climate Normals for 1991–2020: the dates on which the chance of a later spring (or earlier fall) temperature of 32 °F is 50%, 10% and 90%, and the median frost-free season. For each ZIP code we take the nearest of 6,518 stations with these statistics, up to 93 miles (150 km) away; farther than that we show no date. The page names the station, its distance and elevation.
Where a 32 °F frost doesn't occur in most winters (much of Florida, southern Arizona and California, Hawaii, Puerto Rico), the median dates are meaningless, so we say that frost is rare instead of printing them.
Climate
Monthly average highs and lows, yearly hot days (90 °F or more), freezing nights (32 °F or less) and growing degree days (base 50 °F) come from the nearest NOAA station with temperature normals; monthly precipitation and snowfall from the nearest station with precipitation normals (there are about twice as many). Both are NOAA NCEI U.S. Climate Normals 1991–2020, and each page names the stations.
Frost forecast
The 7-night frost forecast is loaded live in your browser from the National Weather Service (api.weather.gov, public domain), together with any active Frost Advisory or Freeze Warning for the spot. We flag nights at 36 °F or below as “frost possible”, 32 °F as freeze and 28 °F as hard freeze. It is not a warning service; official warnings are on weather.gov.
Soil
Soil comes from the USDA NRCS Soil Survey Geographic database (SSURGO), queried through Soil Data Access at the center point of each ZIP code: the largest soil component of the map unit there (built-over “urban land” is skipped when a natural soil is listed underneath) and its top layer — texture, pH (1:1 water), organic matter — plus drainage class, hydrologic group and farmland class. Citation: Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic (SSURGO) Database. Available online. Accessed 2026-10-29.
Spring arrival
“When spring arrived” compares this year's first-leaf Spring Index with its 1991–2020 average at each ZIP code (lower 48 states, 4 km grid). Source: USA National Phenology Network, www.usanpn.org — Spring Indices (CC BY 4.0). Citation: USA National Phenology Network. 2026. Spring Indices, Current Year and 30-year Average, first leaf. USA-NPN, Tucson, Arizona, USA.
Native plants
Native plant suggestions come from the USDA NRCS PLANTS Database: species recorded in the state, native to the region, with a USDA plant guide or fact sheet and a “Temperature, Minimum” value at or below the cold end of the zone. Citation: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov). National Plant Data Team, Greensboro, NC USA. We link to each plant's PLANTS profile and do not copy photos.
Maps and outlines
State outlines: U.S. Census Bureau cartographic boundaries (2023). ZIP code areas: Census ZIP Code Tabulation Areas (ZCTA, 2020), simplified to about 40 m. A ZCTA approximates the delivery area of a ZIP code; PO-box ZIP codes have no area and are shown as a point.
Planting calendar
The calendar applies the week offsets U.S. cooperative extension services publish (for example, start tomatoes indoors 6–8 weeks before the last frost and transplant 1–3 weeks after it) to the station's median frost dates. It is a starting point; soil temperature and the season's weather matter more than the calendar.
ZIP code locations
Each ZIP code is placed at the U.S. Census Bureau ZCTA internal point (2024 Gazetteer). For PO-box and single-building ZIP codes with no Census area we use the GeoNames postal-code point. Place and county names come from GeoNames (CC BY 4.0).
Download
zip-zones.csv — one row per ZIP code: place, state, 2023 zone and temperature range, 2012 zone, median last and first frost, 10%-risk dates, growing season, NOAA station and distance, summer high, winter low, hot days, freezing nights, growing degree days, precipitation and snowfall. Free to use under CC BY 4.0; please credit “plantingzonemap.com” and the original sources below.
How to cite
Planting Zone Map (plantingzonemap.com), 2026. Hardiness zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 29 Oct 2026. Frost dates: NOAA NCEI U.S. Climate Normals 1991–2020.
Who runs this site
Planting Zone Map is built by Digital Dynamics Kft., a small map and data studio (Hungary, EU), which also runs Tornado Live Map. It is independent and not affiliated with the USDA, Oregon State University or NOAA. Corrections are welcome: info@digitaldynamics.hu.