Plant Hardiness Zone
Find the hardiness zone for a location to guide outdoor planting choices.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, Chicago gardens sit in zone 6a on the 2023 USDA map, where average winter lows reach −10 to −5 °F (−23.3 to −20.6 °C) — the number printed on every seed packet sold there.
How to use Plant Hardiness Zone
One winter number decides what survives:
The Plant Hardiness Zone finder tells you the USDA hardiness zone of any location — the band based on the average coldest winter temperature, which decides which perennial plants survive outdoors there. Enter the place and read its zone and half-zone — the code printed on plant labels.
- 1Locate your garden or farm.
- 2Read the hardiness zone.
What people use Plant Hardiness Zone for
1. Buying perennials that live
A shrub rated 'zones 5–8' is a promise about winter cold. Check your zone before the nursery run and the promise becomes testable — gardeners in zone 6a buy differently from zone 8a.
2. Moving house, new climate
Relocating gardeners bring habits from the old zone. The new zone recalibrates what 'hardy' means before the first beloved plant dies learning it.
3. Reading the 2023 map's shifts
The 2023 USDA revision (1991–2020 data) moved roughly half the US map about half a zone warmer than 2012. Your zone from memory may be a zone out of date.
4. Orchards and landscaping plans
Trees are decades-long bets placed on winter minima. Zone first, cultivar second — with microclimate judgement layered on top, as the FAQs insist.
Worked examples
Zone 6b means the average annual extreme minimum winter temperature is −5 to 0 °F (−20.6 to −17.8 °C). Not the coldest ever recorded — the average of each year's coldest night across three decades. Plants rated to zone 6 survive the typical worst night, not the legendary one.
Minneapolis moved from 4b on the 2012 map to about 5a on the 2023 map — winters' coldest nights averaged roughly 5 °F warmer in the newer data window. Gardeners there felt it before the map admitted it.
USDA zones — winter minimum bands
Each full zone spans 10 °F of average annual extreme minimum temperature; half-zones (a/b) split it into 5 °F steps.
| Zone | Average winter low | In Celsius |
|---|---|---|
| 4a | −30 to −25 °F | −34.4 to −31.7 °C |
| 6b | −5 to 0 °F | −20.6 to −17.8 °C |
| 7a | 0 to 5 °F | −17.8 to −15.0 °C |
| 8b | 15 to 20 °F | −9.4 to −6.7 °C |
| 10a | 30 to 35 °F | −1.1 to 1.7 °C |
| 13b | 65 to 70 °F | 18.3 to 21.1 °C |
The 2023 USDA map (based on 1991–2020 data from thousands of weather stations) is the current edition. Britain and Europe use their own hardiness framings — RHS ratings and European zone adaptations echo the same idea.
Hardiness zones guide winter survival
USDA-style zones estimate how cold winters typically get, which helps choose perennials and trees. Summer heat, soil, and watering still decide whether a plant thrives.
City centres are often milder than rural stations a few miles away. When in doubt, favour plants rated for a colder zone than the map suggests.
How to interpret the result
The most common errors come from using a correct result to answer the wrong geographic question. Keep these points in mind for Plant Hardiness Zone:
- Include your height inputs explicitly (eye height, mast height, deck level) when sharing visibility results: the same hill answers differently for a child, an adult and a 10 m antenna, and unstated heights make numbers unreproducible.
- Treat climate and hardiness outputs as 30-year character, not this year's weather: a zone tells you what winters usually allow, and microclimates — walls, slopes, urban heat — shift a real garden half a zone either way.
Limits & appropriate use
Terrain intelligence carries one dominant limit: the model sees bare earth at ~90 m spacing with metres of vertical error, and is blind to canopies, walls and wires. Every downstream answer inherits it — profiles show terrain truth with noisy amplitude, line-of-sight verdicts are pending trees, horizons assume open ground, and solar radiation averages assume an unshaded panel. The second limit is temporal: climate letters and hardiness zones are thirty-year character, not this year's behaviour, and seismicity is a mood, not a hazard model. Each result here is printed with its recipe precisely so these boundaries travel with the number.
The value proposition is screening-grade truth at zero cost: orientation for sites, gardens, antennas, shoots and curiosity, with the upgrade points clearly marked. When money or safety attaches to the answer — tower siting, flood insurance, structural shading, avalanche terrain — the escalation is professional: licensed survey, certified shade studies, regulatory flood determinations and geological hazard services. A good free tool makes that ladder visible instead of pretending to be the top of it.
- Construction and tower siting → licensed topographic survey.
- Flood decisions → regulatory determinations (FEMA/FIRM in the US).
- Solar finance → certified shade and production studies.
Data & methodology
The workspace averages annual minimum temperatures from complete 2000–2023 Open-Meteo archive data and maps the result to broad 10°F bands; this is not the official USDA map.
For source details, licences and model limitations, see Data Sources and Methodology.
Key terms worth knowing
- Antipode
- The diametrically opposite point; latitude flips, longitude shifts 180°.
- Köppen class
- The letter-code climate system from temperature/precipitation thresholds.
Editorial guidance: MapBench explains the method and limitations so the tool can be used as a transparent reference, not as a black-box answer. For legal boundaries, safety-critical routing, surveying, engineering, regulated decisions or official statistics, verify the result with the responsible authority or a qualified professional.
Category: Earth Science. Results are intended for everyday analysis and planning unless a page explicitly states otherwise.
Method, assumptions & limits
- This tool’s method
- The workspace averages annual minimum temperatures from complete 2000–2023 Open-Meteo archive data and maps the result to broad 10°F bands; this is not the official USDA map.
- Before relying on the answer
- Check the location, height units and any model options shown by this calculator. A terrain lookup and a geometric Earth model answer different questions.
- What the result cannot establish
- Local terrain, atmospheric conditions and source resolution can matter more than numerical rounding. Do not use a planning result for safety-critical work.
Coverage: US focused. Search, basemap and external data requests may use third-party services; browser-based does not mean every operation is offline. Read the source and licence notes, calculation methodology and privacy policy. If a result looks inconsistent, report a correction with the inputs and mode used.
Frequently asked questions
Clear answers about the calculation, accuracy and appropriate use.
Only US?
Focused on USDA-style zones; microclimates and urban heat still matter.
Is this suitable for engineering or legal decisions?
Treat the result as planning or educational context unless the page explicitly says otherwise. Engineering, hazard and legal decisions should use authoritative specialist data.
Why can terrain data differ between sources?
Elevation and earth datasets vary in resolution, collection date and processing method. Small local features may not be represented equally.
Can I verify the data source?
Yes. MapBench documents major providers and methodology on the Data Sources and Methodology pages.
Does the zone use the coldest night ever?
No — it averages the single coldest night of each winter across the data period. A once-in-50-years freeze goes below the zone's floor; that is why experienced gardeners near a boundary buy half a zone of margin.
Microclimates — my garden is warmer.
Often true: south walls, city heat islands, cold-air drainage and snow cover shift a garden's reality by half a zone or more either way. The map gives the regional baseline; your thermometer keeps the local truth.
Zone says nothing about summer?
Correct — heat, humidity, rainfall and season length are separate axes (heat-zone maps exist for the first). Two zone-7 gardens, coastal Oregon and inland Georgia, garden very differently.
Canada and Europe?
Canada publishes its own hardiness map on a related but distinct formula; Europe is often described with USDA-equivalent zones in catalogues. This page speaks the USDA system named on North American labels.
Container plants?
Pots expose roots to far colder temperatures than the ground feels — treat container plants as needing roughly two zones of extra hardiness, the nurseryman's rule of thumb.
How often does the map change?
USDA revised in 2012 and 2023 as data windows roll forward. Zones are climate statistics, not borders — expect slow drift, and re-check before big plantings.
Snow cover helps?
Reliably: snow is insulation, and perennials under a steady snowpack survive air temperatures well below their rating. The zone counts air temperature only — one more reason locals out-garden maps.
First and last frost dates?
Different data (spring/autumn averages) and just as decision-relevant for annuals — zones govern perennial survival through winter, frost dates govern the growing season's bookends.
Related tools and resources
The ground beneath the garden: the Elevation Finder; flood context for the plot: the Flood Zone Check; your spot: My Elevation.
More free tools
Sources, methodology & editorial trust
- ✓ Browser-first processing where supported
- ✓ External sources are documented
- ✓ No account required for public tools
- ✓ Review data sources
Calculations are documented with their assumptions, limitations and source context rather than presented as unexplained answers.
Reviewed and maintained by Aryan Khan, Founder & Editor of MapBench.
Part of our elevation & terrain hub
Plant Hardiness Zone sits in the elevation & terrain cluster, alongside 40 other tools that answer neighbouring questions with different methods or datasets.
You may also need
When this answer is only part of the job, these clusters cover the next step.
Read the guide behind this tool
Hardiness Zones & Climate Codes: Will It Grow Here? — Hardiness zones, climate classifications and microclimates answer different questions. How to use them without treating one map as the whole garden.