USDA Hardiness Zone Map Guide: Every Zone Explained with Planting Data
The USDA Plant Hardiness Zone Map is the standard reference for determining which plants can survive winter in a given location. The map divides the U.S. into 13 zones based on average annual extreme minimum winter temperature, using 30 years of data (1991–2020) from NOAA weather stations.
This guide covers every zone with temperature ranges, typical growing season lengths, representative cities, and recommended vegetable crops. All data is sourced from the USDA Agricultural Research Service and NOAA National Centers for Environmental Information.
Complete Zone Temperature Reference
Each zone spans a 10°F range, split into "a" (colder half) and "b" (warmer half) sub-zones of 5°F each.
| Zone | Min Temp (°F) | Min Temp (°C) | Typical Growing Season | Example Locations |
|---|---|---|---|---|
| 1a | -60 to -55 | -51 to -48 | ~60 days | Fairbanks, AK (interior) |
| 1b | -55 to -50 | -48 to -46 | ~75 days | Central Alaska |
| 2a | -50 to -45 | -46 to -43 | ~80 days | Prudhoe Bay, AK |
| 2b | -45 to -40 | -43 to -40 | ~90 days | International Falls, MN |
| 3a | -40 to -35 | -40 to -37 | ~100 days | Duluth, MN; Anchorage, AK |
| 3b | -35 to -30 | -37 to -34 | ~110 days | Fargo, ND; Bangor, ME |
| 4a | -30 to -25 | -34 to -32 | ~120 days | Minneapolis, MN; Burlington, VT |
| 4b | -25 to -20 | -32 to -29 | ~130 days | Rapid City, SD; Concord, NH |
| 5a | -20 to -15 | -29 to -26 | ~140 days | Des Moines, IA; Denver, CO |
| 5b | -15 to -10 | -26 to -23 | ~155 days | Chicago, IL; Salt Lake City, UT |
| 6a | -10 to -5 | -23 to -21 | ~165 days | St. Louis, MO; Hartford, CT |
| 6b | -5 to 0 | -21 to -18 | ~175 days | Nashville, TN; Portland, OR |
| 7a | 0 to 5 | -18 to -15 | ~185 days | Oklahoma City, OK; Virginia Beach, VA |
| 7b | 5 to 10 | -15 to -12 | ~200 days | Little Rock, AR; Raleigh, NC |
| 8a | 10 to 15 | -12 to -9 | ~215 days | Dallas, TX; Seattle, WA |
| 8b | 15 to 20 | -9 to -7 | ~230 days | Austin, TX; Savannah, GA |
| 9a | 20 to 25 | -7 to -4 | ~260 days | Houston, TX; Sacramento, CA |
| 9b | 25 to 30 | -4 to -1 | ~290 days | Orlando, FL; Phoenix, AZ |
| 10a | 30 to 35 | -1 to 2 | ~320 days | Miami, FL; San Diego, CA |
| 10b | 35 to 40 | 2 to 4 | ~340 days | Naples, FL; Coastal SoCal |
| 11a | 40 to 45 | 4 to 7 | Year-round | Key West, FL |
| 11b | 45 to 50 | 7 to 10 | Year-round | Honolulu, HI |
| 12a | 50 to 55 | 10 to 13 | Year-round | Hawaii (lower elevations) |
| 12b | 55 to 60 | 13 to 16 | Year-round | Puerto Rico (interior) |
| 13a | 60 to 65 | 16 to 18 | Year-round | Puerto Rico (coastal) |
| 13b | 65 to 70 | 18 to 21 | Year-round | U.S. Virgin Islands |
Source: USDA Plant Hardiness Zone Map, 2023 revision. Growing season lengths are approximate averages and vary by specific location, elevation, and microclimate.
Best Vegetables by Zone Group
Different zones favor different crops based on growing season length and temperature extremes. Here's what works best in each range.
Zones 3–4: Short Season (80–130 frost-free days)
Focus on cold-hardy, fast-maturing varieties. Start warm-season crops indoors 6–8 weeks before last frost.
- Best performers: Kale, lettuce, spinach, peas, radishes, potatoes, carrots, beets, turnips
- Possible with protection: Tomatoes (early varieties like 'Glacier', 55 days), bush beans, zucchini
- Skip or greenhouse only: Watermelon, sweet potatoes, okra, long-season peppers
- Typical last frost: Mid-May to early June
- Typical first frost: Mid-September to early October
Zones 5–6: Moderate Season (140–175 frost-free days)
The sweet spot for most vegetable gardening. Nearly all common vegetables succeed here with proper timing.
- Best performers: Tomatoes, peppers, cucumbers, beans, corn, squash, most root vegetables
- Possible with care: Watermelon (short-season varieties), sweet potatoes (in zone 6)
- Fall/winter crops: Garlic (plant in October), kale, spinach, cold frames extend season
- Typical last frost: Late April to mid-May
- Typical first frost: Late September to late October
Zones 7–8: Long Season (185–230 frost-free days)
Long warm seasons enable succession planting and fall vegetable gardens.
- Best performers: Everything above plus okra, sweet potatoes, southern peas, melons
- Advantage crops: Two tomato plantings possible (spring + late summer in zone 8)
- Winter gardening: Lettuce, spinach, kale, carrots, beets grow through mild winters
- Typical last frost: Mid-March to mid-April
- Typical first frost: Late October to late November
Zones 9–10: Near Year-Round (260–340 frost-free days)
Summer heat is often the limiting factor, not cold. Many cool-season crops grow best in fall/winter.
- Best performers: Tropical vegetables, sweet potatoes, okra, peppers year-round
- Timing shift: Cool-season crops (lettuce, peas, broccoli) planted in fall, harvested winter/spring
- Summer challenges: Tomatoes often stop setting fruit above 95°F; plant early or use heat-tolerant varieties
- Typical last frost: January to February (if any)
- Typical first frost: December to January (if any)
2023 Map Update: What Changed
The USDA released an updated Plant Hardiness Zone Map on November 15, 2023, replacing the 2012 version. Key changes:
- Data period: 1991–2020 (replacing 1976–2005), a 15-year shift forward
- Resolution: Increased from 1-mile to 0.5-mile grid cells, enabling more precise local determinations
- Zone shifts: Approximately 49% of the contiguous U.S. moved to a warmer half-zone
- New zones: Zones 12b and 13 (a and b) were added, covering Hawaii and U.S. territories
- Station count: Increased from ~8,000 to ~13,000 weather stations
The average minimum extreme temperature across the U.S. increased by approximately 2.5°F compared to the 2012 map. This means some perennial plants previously considered marginally hardy in your area may now be viable. However, individual cold snaps can still kill plants rated for your zone, as the map shows averages, not guarantees.
Zones vs. Other Climate Indicators
| Factor | USDA Zone Tells You | What You Also Need |
|---|---|---|
| Winter cold survival | ✅ Yes | — |
| Summer heat tolerance | ❌ No | AHS Heat Zone Map |
| When to plant vegetables | ❌ No (indirectly) | Local frost dates (look yours up) |
| Rainfall / irrigation needs | ❌ No | Local climate data, NOAA |
| Soil type | ❌ No | USDA Web Soil Survey |
| Growing season length | ⚠️ Rough correlation | Frost date records |
| Day length / sun intensity | ❌ No | Latitude-based calculations |
Frequently Asked Questions
Enter your zip code at planthardiness.ars.usda.gov to find your exact zone. The 2023 map update shifted about half the U.S. a half-zone warmer compared to the 2012 map.
There are 13 main zones (1–13), each split into "a" and "b" sub-zones, for 26 total sub-zones. Each sub-zone covers a 5°F range of average annual extreme minimum temperature.
The 2023 map uses 1991–2020 climate data (replacing 1976–2005). Approximately 49% of the contiguous U.S. shifted to a warmer half-zone, reflecting both a longer data window and actual warming trends. Resolution also improved from 1-mile to 0.5-mile grids.
Indirectly. Zones indicate winter cold, which matters most for perennials. For annual vegetables, your frost dates and growing season length are more directly useful. Zone is a useful shorthand for general climate, but it doesn't tell you when to plant tomatoes.
Hardiness zones measure average minimum winter temperature. The AHS (American Horticultural Society) Heat Zone Map measures average number of days above 86°F (30°C). A plant rated for zone 5 hardiness may still fail in a zone 5 location with extreme summer heat. Unfortunately, heat zone ratings are less commonly listed by nurseries.
Get personalized planting dates based on your zip code's frost data, not just your zone number.
Try the free planting calendar →
Sources
- USDA Agricultural Research Service. Plant Hardiness Zone Map, 2023. planthardiness.ars.usda.gov
- NOAA National Centers for Environmental Information. Climate Normals, 1991–2020. ncei.noaa.gov
- Daly, C. et al. (2012). "Development of a New USDA Plant Hardiness Zone Map for the United States." Journal of Applied Meteorology and Climatology, 51(2), 242–264.
- American Horticultural Society. AHS Plant Heat Zone Map. ahsgardening.org