USDA Plant Hardiness Zone Lookup & Complete Guide
Your hardiness zone is the single most important number for deciding what to plant and when. It tells you how cold your winters get, which determines which perennials survive and when it's safe to put transplants outside.
The USDA updated its Plant Hardiness Zone Map in November 2023 using 30 years of temperature data (1991–2020). About half the country shifted to a warmer half-zone. If you haven't checked your zone since 2012, it may have changed.
🌱 Quick lookup: Use our Planting Calendar Tool — enter your zip code and it automatically finds your zone and gives you planting dates for 40+ vegetables.
All USDA Hardiness Zones at a Glance
| Zone | Min Winter Temp (°F) | Min Winter Temp (°C) | Example Locations | Approx. Growing Season |
|---|---|---|---|---|
| 1a | -60 to -55 | -51 to -48 | Interior Alaska (Fairbanks) | ~75 days |
| 1b | -55 to -50 | -48 to -46 | Northern Alaska | ~80 days |
| 2a | -50 to -45 | -46 to -43 | Prudhoe Bay, AK | ~85 days |
| 2b | -45 to -40 | -43 to -40 | Fairbanks outskirts, AK | ~90 days |
| 3a | -40 to -35 | -40 to -37 | International Falls, MN | ~100 days |
| 3b | -35 to -30 | -37 to -34 | Duluth, MN; Tomahawk, WI | ~110 days |
| 4a | -30 to -25 | -34 to -32 | Minneapolis, MN; Bismarck, ND | ~120 days |
| 4b | -25 to -20 | -32 to -29 | Des Moines, IA; Burlington, VT | ~130 days |
| 5a | -20 to -15 | -29 to -26 | Chicago, IL; Boston, MA | ~140 days |
| 5b | -15 to -10 | -26 to -23 | Denver, CO; Detroit, MI | ~150 days |
| 6a | -10 to -5 | -23 to -21 | St. Louis, MO; Hartford, CT | ~160 days |
| 6b | -5 to 0 | -21 to -18 | Nashville, TN; Portland, OR | ~175 days |
| 7a | 0 to 5 | -18 to -15 | Oklahoma City, OK; Richmond, VA | ~190 days |
| 7b | 5 to 10 | -15 to -12 | Little Rock, AR; Raleigh, NC | ~200 days |
| 8a | 10 to 15 | -12 to -9 | Dallas, TX; Seattle, WA | ~220 days |
| 8b | 15 to 20 | -9 to -7 | Austin, TX; Savannah, GA | ~240 days |
| 9a | 20 to 25 | -7 to -4 | Houston, TX; Jacksonville, FL | ~260 days |
| 9b | 25 to 30 | -4 to -1 | Orlando, FL; Phoenix, AZ | ~280 days |
| 10a | 30 to 35 | -1 to 2 | Miami, FL; San Diego, CA | ~300 days |
| 10b | 35 to 40 | 2 to 4 | Key West, FL; Naples, FL | ~320 days |
| 11a | 40 to 45 | 4 to 7 | Honolulu, HI | ~340 days |
| 11b | 45 to 50 | 7 to 10 | Hawaii (coastal) | ~350 days |
| 12a | 50 to 55 | 10 to 13 | Puerto Rico, US Virgin Islands | Year-round |
| 12b | 55 to 60 | 13 to 16 | Puerto Rico (coastal) | Year-round |
| 13a | 60 to 65 | 16 to 18 | Puerto Rico (low elevation) | Year-round |
| 13b | 65 to 70 | 18 to 21 | Tropical US territories | Year-round |
Source: USDA Agricultural Research Service, Plant Hardiness Zone Map (2023 revision), planthardiness.ars.usda.gov
What Changed in the 2023 Update
The 2023 map used 30 years of data (1991–2020) compared to the 2012 map which used 1976–2005 data. Key changes:
- About half of the US shifted to a warmer half-zone (5°F warmer)
- Zone 13 was added for the first time (tropical US territories)
- Much of the Southeast and parts of the Midwest saw the biggest shifts
- The resolution improved from half-mile to quarter-mile grid squares
This doesn't mean you can suddenly grow oranges in Tennessee. But it does mean your frost dates may be slightly later in fall and earlier in spring than older references suggest.
How to Use Your Zone for Planting Decisions
Your zone number appears on nearly every plant tag and seed packet. Here's how to read it:
- Perennials and trees: The zone rating tells you if the plant will survive your winter. A plant rated "zones 5–9" will survive winter in zones 5 through 9 but may die in zone 4.
- Annuals and vegetables: Zone is less about survival and more about timing. Your zone determines your frost dates, which determine when to start seeds and transplant.
- Seed starting: Count backward from your last frost date. Most vegetables need 6–8 weeks indoors. See our seed starting guide.
Average Last Frost Dates by Zone
| Zone | Avg Last Spring Frost | Avg First Fall Frost |
|---|---|---|
| 3 | May 15 – June 1 | September 1–15 |
| 4 | May 1–15 | September 15 – October 1 |
| 5 | April 15 – May 1 | October 1–15 |
| 6 | April 1–15 | October 15 – November 1 |
| 7 | March 15 – April 1 | November 1–15 |
| 8 | March 1–15 | November 15 – December 1 |
| 9 | February 15 – March 1 | December 1–15 |
| 10+ | Frost-free or rare frost | Frost-free or rare frost |
Source: NOAA National Centers for Environmental Information, averaged station data
For exact frost dates by your zip code, see our frost date lookup.
Most Popular Vegetables by Zone Compatibility
| Vegetable | Min Zone (Outdoor) | Days to Harvest | Planting Guide |
|---|---|---|---|
| Tomatoes | 3+ (after frost) | 60–85 | By zone |
| Peppers | 4+ (after frost) | 60–90 | Guide |
| Lettuce | 2+ (cool season) | 30–60 | Spring planting |
| Cucumbers | 4+ (after frost) | 50–70 | Schedule |
| Squash | 3+ (after frost) | 50–100 | Spring vegs |
| Garlic | 3+ (fall planted) | 240+ | Fall guide |
🗓️ Get your personalized planting dates: Use our free Planting Calendar — enter your zip code for custom schedules for 40+ crops.
Data from the 2023 USDA Plant Hardiness Zone Map. If you cite this reference, please link back to this page.