Free tool · Tools · 2023 USDA zones
Hardiness zone by ZIP code
Type a ZIP code to get its USDA plant hardiness zone from the 2023 map, the average coldest winter night behind it, and which plant tags to trust. Covers 40,502 ZIP codes in all 50 states and Puerto Rico.
Lock Haven (17745) is zone 6a: the average coldest night of the year there is −10°F to −5°F, from 1991–2020 data. Plants rated for zone 6 or lower should make it through a typical winter. Checked Nov. 13, 2026.
Find your zone
A ZIP code covers a lot of ground, and hilltops, valleys and city blocks inside it can differ from its zone. For an exact address, check the official USDA map.
| Average coldest nightMean of each winter’s lowest temperature, 1991–2020 | — |
| Plant tags to trustHardy to this zone or colder | — |
| Nearby ZIPsSame first three digits | — |
Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 ZIP code listing published by the PRISM Group at Oregon State University, which built the 2023 USDA map.
What each zone means
Each zone is a 10°F band of the average coldest winter night, and each half zone (a or b) is 5°F. The “a” half is the colder one. A plant tag that says “hardy to zone 6” should survive a typical winter in zone 6 and in any warmer zone.
| Zone | Average coldest night |
|---|---|
| 1a | −60°F to −55°F |
| 1b | −55°F to −50°F |
| 2a | −50°F to −45°F |
| 2b | −45°F to −40°F |
| 3a | −40°F to −35°F |
| 3b | −35°F to −30°F |
| 4a | −30°F to −25°F |
| 4b | −25°F to −20°F |
| 5a | −20°F to −15°F |
| 5b | −15°F to −10°F |
| 6a | −10°F to −5°F |
| 6b | −5°F to 0°F |
| 7a | 0°F to 5°F |
| 7b | 5°F to 10°F |
| 8a | 10°F to 15°F |
| 8b | 15°F to 20°F |
| 9a | 20°F to 25°F |
| 9b | 25°F to 30°F |
| 10a | 30°F to 35°F |
| 10b | 35°F to 40°F |
| 11a | 40°F to 45°F |
| 11b | 45°F to 50°F |
| 12a | 50°F to 55°F |
| 12b | 55°F to 60°F |
| 13a | 60°F to 65°F |
| 13b | 65°F to 70°F |
Pennsylvania hardiness zones
Pennsylvania ZIP codes on the 2023 list run from zone 5b to zone 8a. In central Pennsylvania: Lock Haven (17745) is 6a, State College (16801) is 6b, Williamsport (17701) is 6a, Bellefonte (16823) is 6b.
Zone tells you how cold winter gets, not when it’s safe to plant. For last and first frost dates, see Pennsylvania rainfall, snowfall and frost dates by town. For zones across the country, see planting zones by state.
Using your zone
Use the zone to rule plants out, not in. A plant rated colder than your zone handles winter; one rated warmer is a gamble. Wind, a south-facing wall or a frost pocket can make one spot in your yard warmer or colder than the zone suggests. Pair the zone with a soil test and your frost dates before you buy.
Questions
What planting zone is my ZIP code?
Type your ZIP code in the tool above. It returns the 2023 USDA zone for that ZIP from the PRISM Group at Oregon State University’s ZIP code listing, plus the average coldest winter night behind it.
What zone is Lock Haven, PA?
Lock Haven (17745) is zone 6a on the 2023 USDA map, an average coldest night of −10°F to −5°F.
Did my zone change on the 2023 map?
Maybe. USDA says about half of the country shifted to the next warmer half zone compared with the 2012 map, and the other half stayed the same. USDA also says the updates are not necessarily a sign of climate change.
What is the difference between zone 6a and 6b?
Zone 6a’s average coldest night is −10°F to −5°F and zone 6b’s is −5°F to 0°F. The “a” half zone is always the colder one.
Is this the official USDA map?
No. It uses the 2023 ZIP code listing from the PRISM Group at Oregon State University, which built the official map. For an exact address, use the USDA map at planthardiness.ars.usda.gov.
Sources: PRISM Group, Oregon State University, Plant Hardiness Zone GIS datasets and ZIP code listings (2023); USDA ARS, Plant Hardiness Zone Map; USDA ARS, 2023 map announcement. Checked Nov. 13, 2026.
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See landscape designAll toolsIn central PA? We build patios, retaining walls and landscapes from Lock Haven to State College and Williamsport: Lock Haven, Williamsport, State College. Also: soil by ZIP code, mulch and topsoil calculator.
Muthler Landscaping & Construction LLC · 913 Bellefonte Ave, Lock Haven, PA 17745 · (570) 397-9800 · PA HIC #PA212584. Zone data © Oregon State University, used under PRISM’s terms; not the official USDA map.