Hardiness Zones Explained
A hardiness zone is a band of winter cold. The USDA map divides the country into zones by the average annual extreme winter low temperature, so a plant rated for your zone can be expected to survive your typical coldest night of the year.
The zones at a glance
Each zone spans 10 °F, split into a colder a half and a warmer b half of 5 °F each. The figures below are the 2023 USDA Plant Hardiness Zone Map bands. Tap a zone for its page, with where it occurs and real yards growing in it.
| Zone | Winter low (°F) | Winter low (°C) | a / b halves (°F) | Yards on YardShare |
|---|---|---|---|---|
| Zone 1 | -60 to -50 | -51.1 to -45.6 | 1a -60 to -55 / 1b -55 to -50 | 12 |
| Zone 2 | -50 to -40 | -45.6 to -40 | 2a -50 to -45 / 2b -45 to -40 | 9 |
| Zone 3 | -40 to -30 | -40 to -34.4 | 3a -40 to -35 / 3b -35 to -30 | 10 |
| Zone 4 | -30 to -20 | -34.4 to -28.9 | 4a -30 to -25 / 4b -25 to -20 | 37 |
| Zone 5 | -20 to -10 | -28.9 to -23.3 | 5a -20 to -15 / 5b -15 to -10 | 277 |
| Zone 6 | -10 to 0 | -23.3 to -17.8 | 6a -10 to -5 / 6b -5 to 0 | 354 |
| Zone 7 | 0 to 10 | -17.8 to -12.2 | 7a 0 to 5 / 7b 5 to 10 | 366 |
| Zone 8 | 10 to 20 | -12.2 to -6.7 | 8a 10 to 15 / 8b 15 to 20 | 368 |
| Zone 9 | 20 to 30 | -6.7 to -1.1 | 9a 20 to 25 / 9b 25 to 30 | 354 |
| Zone 10 | 30 to 40 | -1.1 to 4.4 | 10a 30 to 35 / 10b 35 to 40 | 167 |
| Zone 11 | 40 to 50 | 4.4 to 10 | 11a 40 to 45 / 11b 45 to 50 | 14 |
| Zone 12 | 50 to 60 | 10 to 15.6 | 12a 50 to 55 / 12b 55 to 60 | 3 |
What a zone does and does not tell you
A zone measures one thing only: how cold winter gets. It says nothing about summer heat, rainfall, humidity, soil, or the sheltered and exposed corners of your own yard, and all of those decide what thrives. The full researched guide, with the map's history, how to find your zone, and what the data does not capture, is being built as the next step of this collection.
Data: 2023 USDA Plant Hardiness Zone Map (USDA and PRISM Climate Group, Oregon State University). Yard counts are live from the YardShare archive and count yards whose zone tag is set.