If a plant tag says “hardy to zone 6,” that number isn’t arbitrary, it’s a direct reference to the USDA Plant Hardiness Zone Map, the standard system nearly every nursery, seed catalog, and gardening guide in the country uses to answer one question: will this plant survive winter where you live.
Quick Answer: USDA hardiness zones are 13 geographic bands across the U.S. based on the average annual extreme minimum winter temperature, each spanning a 10°F range and split into “a” and “b” half-zones 5°F apart. Zone 1 is the coldest (Alaska’s interior), Zone 13 is the warmest (parts of Hawaii and Puerto Rico). Find your zone using the official USDA Plant Hardiness Zone Map by entering your ZIP code, then match it against a plant’s tag or listing before planting anything perennial.
What Are USDA Hardiness Zones, Exactly?
So what are the USDA hardiness zones, in plain terms? USDA plant hardiness zones are a classification system that divides the United States and its territories into 13 zones based on the average coldest temperature each area typically experiences in a year, measured over a 30-year period. The map is produced and maintained by the U.S. Department of Agriculture’s Agricultural Research Service (ARS), most recently updated in 2023 using data through 2020.
Each zone represents a 10°F range of average annual minimum temperature, and each zone is further split into an “a” half (colder) and “b” half (warmer), 5°F apart. So Zone 7a and Zone 7b are both “Zone 7,” but 7a runs 0°F to 5°F while 7b runs 5°F to 10°F, a distinction that matters for plants near their cold tolerance limit.
The system exists to answer a narrow but genuinely useful question: will a perennial plant, tree, or shrub survive the winter in a given location. It does not account for summer heat, humidity, soil type, rainfall, or elevation-driven microclimates, which is why two spots in the same zone can still have very different growing conditions overall.
USDA Hardiness Zones Map: How to Find Yours
The official USDA Plant Hardiness Zone Map lets you enter a ZIP code and get your exact zone and half-zone instantly. It’s the authoritative source, and it’s free to use directly on USDA’s site rather than relying on a secondhand chart that may reflect the outdated pre-2023 map.
A few things worth knowing before you look yours up:
Your zone can span a wide area, or change over a short distance. Elevation, proximity to large bodies of water, and urban heat effects can shift the effective zone within the same city or county, particularly in mountainous or coastal regions.
The 2023 update moved many areas up half a zone. Roughly half the country shifted into a slightly warmer zone compared to the 2012 map, reflecting warmer winter temperature averages over the more recent 30-year period, not necessarily a prediction about future climate.
Zone alone doesn’t guarantee a plant will thrive. It tells you whether a plant can survive your coldest winter temperatures. Sun exposure, soil drainage, and summer heat still matter for whether it actually grows well.
The 13 USDA Hardiness Zones
| Zone | Avg. Minimum Temp | General Region |
|---|---|---|
| 1 | -60°F to -50°F | Interior Alaska |
| 2 | -50°F to -40°F | Alaska, northernmost Minnesota |
| 3 | -40°F to -30°F | Upper Midwest, northern Rockies |
| 4 | -30°F to -20°F | Northern Plains, Great Lakes, New England |
| 5 | -20°F to -10°F | Midwest, Mid-Atlantic, Mountain West |
| 6 | -10°F to 0°F | Ohio Valley, Mid-Atlantic, Pacific Northwest |
| 7 | 0°F to 10°F | Upper South, Mid-Atlantic coast, parts of the Southwest |
| 8 | 10°F to 20°F | Deep South, coastal Pacific Northwest |
| 9 | 20°F to 30°F | Gulf Coast, coastal California, north and central Florida |
| 10 | 30°F to 40°F | South Florida, southern California, south Texas coast |
| 11 | 40°F to 50°F | South Florida Keys, parts of Hawaii, coastal Southern California |
| 12 | 50°F to 60°F | Parts of Hawaii, Puerto Rico |
| 13 | 60°F to 70°F | Warmest parts of Hawaii and Puerto Rico |
This table reflects the 13-zone system from the 2023 USDA update. Older charts and plant tags printed before 2023 may still reference the previous 11-zone system, worth checking the date on any source before relying on it.
What to Grow Based on Your Zone
Hardiness zones matter most for perennials, trees, and shrubs, plants expected to survive multiple winters in the ground. They matter far less for annuals like tomatoes, zucchini, and most bedding flowers, since those complete their entire life cycle in a single growing season and die at the end of it regardless of zone.
When shopping for perennials, check the plant tag or listing for a hardiness range, something like “hardy in zones 4-8.” If your zone falls within that range, the plant should survive a typical winter in your area. If your zone is colder than the plant’s stated range, it likely won’t survive outdoors without protection; if it’s warmer, the plant may struggle from insufficient winter chill, which some species need to flower or fruit properly.
USDA Hardiness Zones by State
Zones vary significantly within larger states, since latitude, elevation, and coastal proximity all shift the average minimum temperature. LawnGuru has state-specific breakdowns for several states with meaningful zone variation:
- What Planting Zone Is Ohio?
- What Planting Zone Is Georgia?
- Planting Zones of Pennsylvania
- What Planting Zone Is New Jersey?
- What Planting Zones Are in Florida?
Frequently Asked Questions
How do I find my exact USDA hardiness zone?
Enter your ZIP code directly into the official USDA Plant Hardiness Zone Map. This gives the most precise, current result, more precise than a statewide or regional chart, since zones can vary within a single county.
Are there really 13 USDA hardiness zones now?
Yes, as of the 2023 USDA map update. The system previously had 11 zones; Zones 12 and 13 were added to cover the warmest tropical and subtropical parts of the country, primarily Hawaii and Puerto Rico. Charts still showing only 11 zones are referencing the outdated pre-2023 map.
Do USDA hardiness zones account for summer heat?
No. Hardiness zones are based entirely on average winter minimum temperature. Summer heat tolerance is a separate consideration, sometimes addressed by the American Horticultural Society’s Heat Zone Map, which some plant tags reference alongside the USDA zone.
What’s the difference between a “zone” and a half-zone like “7a” or “7b”?
Each full zone spans a 10°F range and is split into two 5°F half-zones, “a” for the colder half and “b” for the warmer half. A plant listed as hardy to zone 7b but not 7a may struggle in the colder half of that same zone.
Does my hardiness zone guarantee a plant will grow well in my yard?
No, it only tells you whether a plant can survive your typical winter low temperature. Soil type, drainage, sun exposure, humidity, and summer heat all still affect whether a plant actually thrives, hardiness zone is a starting filter, not a full growing guide.
The Bottom Line
USDA hardiness zones answer one specific question, whether a perennial plant can survive your area’s coldest typical winter temperature, and as of the 2023 update, there are 13 of them rather than the 11 many older charts still show. Look up your exact zone directly on USDA’s official map rather than relying on a general regional estimate, then use it as a starting filter alongside sun, soil, and space when choosing what to plant. If you’d rather have a pro handle planting and landscaping decisions for your specific yard, LawnGuru connects you with local landscaping professionals who already know what thrives in your area.
