The USDA Plant Hardiness Zone Map divides the US into 13 zones based on average annual extreme minimum temperatures. Enter your ZIP code to find your zone — the tool uses the 3-digit ZIP prefix to identify your zone from the USDA 2023 PHZM. Zone results include the minimum temperature range in both °F and °C, with a direct link to verify against the USDA official interactive map.
How zones are defined
Each zone spans 10°F of minimum winter temperature.
Each zone is split into "a" (cooler half) and "b" (warmer half), each spanning 5°F.
Zone 7: 0°F to 10°F
Zone 7a: 0°F to 5°F
Zone 7b: 5°F to 10°F
The USDA map is based on 30-year temperature averages from 1991–2020 weather station data.
Practical examples
Example 1: ZIP 10001 (New York City) 3-digit prefix 100 → Zone 7b (5°F to 10°F / −15°C to −12.2°C). Most English roses, hydrangeas, and ornamental grasses rated to zone 7 will reliably overwinter.
Example 2: ZIP 60601 (Chicago) 3-digit prefix 606 → Zone 6a (−10°F to −5°F / −23.3°C to −20.6°C). Many zone 7 perennials won't survive; focus on zone 5b or zone 6 rated plants.
Example 3: ZIP 33101 (Miami) 3-digit prefix 331 → Zone 10a (30°F to 35°F / −1.1°C to 1.7°C). Tropical plants thrive; most temperate perennials and fruit trees requiring winter chill won't fruit properly.
Common mistakes
Using hardiness zone as the only planting guide. Zones describe winter cold — not summer heat, humidity, drought, soil pH, or drainage. A plant rated to zone 7 may still fail in your garden due to summer heat stress or clay soil.
Ignoring microclimates. Your backyard can vary by a full zone from the surrounding area. South-facing walls, reflected heat from pavement, low frost pockets, and urban heat islands all shift effective hardiness. The map gives an average; your site may differ.
Confusing USDA zones with heat zones or Sunset zones. The American Horticultural Society Heat Zone Map and Sunset Western Garden zones use different criteria. A plant rated "USDA zone 8" is a cold-hardiness statement only.
International and regional variations
| System | Used in | Basis |
|---|---|---|
| USDA PHZM (2023) | United States | Average annual extreme minimum temperature (30-year avg) |
| RHS Hardiness Ratings (H1–H7) | United Kingdom | Temperature bands from H1 (tender) to H7 (very hardy, to −20°C) |
| Natural Resources Canada Zones | Canada | Multi-factor index: min temp, frost-free days, rainfall, snow |
| Sunset Climate Zones (1–45) | Western North America | Temperature, humidity, precipitation, and elevation combined |
Quick reference
| Zone | Min temp (°F) | Min temp (°C) | Example cities |
|---|---|---|---|
| 3b | −35 to −30 | −37.2 to −34.4 | Fargo ND, Duluth MN |
| 5b | −15 to −10 | −26.1 to −23.3 | Denver CO, Boston MA |
| 6b | −5 to 0 | −20.6 to −17.8 | St. Louis MO, Philadelphia PA |
| 7b | 5 to 10 | −15 to −12.2 | New York City, Seattle WA |
| 8b | 15 to 20 | −9.4 to −6.7 | Atlanta GA, Portland OR |
| 9b | 25 to 30 | −3.9 to −1.1 | Los Angeles CA, Phoenix AZ |
| 10a | 30 to 35 | −1.1 to 1.7 | Miami FL, Honolulu HI |
For all 26 USDA zones (1a–13b) with temperature ranges and average frost date windows for zones 3–10, see the USDA Plant Hardiness Zone Reference Chart →.