Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 17320 — Fairfield, PA

ZIP code 17320 (Fairfield, Adams County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 28 and the first fall frost October 17.

Where ZIP 17320 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 28
First frostOct 17
2012 zone6b

Was 6b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Fairfield, PA…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Fairfield, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 28median — 50% chance of a later frost
Safe for tender plantsMay 16only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 4
Growing season170 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 16 and returns around October 27.

From the NOAA station Cashtown 1s, PA — 8 miles away, elevation 709 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 17320

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 17 – Mar 31
SpinachSow outdoors · Mar 17 – Apr 7
Broccoli, cabbageStart indoors · Feb 17 – Mar 3
Broccoli, cabbageTransplant · Apr 7 – Apr 21
Onion setsPlant outdoors · Mar 31 – Apr 14
PotatoesPlant outdoors · Apr 7 – Apr 21
LettuceSow outdoors · Mar 31 – Apr 14
Carrots, beetsSow outdoors · Apr 7 – Apr 21
TomatoesStart indoors · Mar 3 – Mar 17
TomatoesTransplant · May 5 – May 19
Peppers, eggplantStart indoors · Feb 17 – Mar 3
Peppers, eggplantTransplant · May 12 – May 26
BeansSow outdoors · May 5 – May 19
Sweet cornSow outdoors · May 5 – May 19
Cucumbers, squashSow outdoors · May 5 – May 19
Fall lettuce, spinachSow outdoors · Aug 22 – Sep 5
GarlicPlant cloves · Oct 3 – Nov 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 17) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 17320 came on Mar 20 — 6 days earlier than the 1991–2020 average (Mar 26).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 7a in Pennsylvania

620 plants native to the lower 48 states, recorded in Pennsylvania, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

Trees 78

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 123

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 212

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 181

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °F

Vines 11

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Fairfield, PA.

Soil in Fairfield, PA

The soil mapped at the center of ZIP 17320 is Hatboro — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
pH5.9moderately acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter3%moderate
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Hatboro silt loam.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 17320; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fairfield, PA

Summer high85 °Faverage high, July
Winter low20 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights134nights a year at 32 °F or less
Growing degree days3,046base 50 °F — the season’s usable heat
Longest day14 h 59 mindaylight on June 21
Shortest day9 h 21 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation48 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 20 °F 37°20° JanFebruary: average high 41 °F, low 21 °F 41°21° FebMarch: average high 49 °F, low 28 °F 49°28° MarApril: average high 62 °F, low 38 °F 62°38° AprMay: average high 72 °F, low 49 °F 72°49° MayJune: average high 81 °F, low 58 °F 81°58° JunJuly: average high 85 °F, low 62 °F 85°62° JulAugust: average high 83 °F, low 60 °F 83°60° AugSeptember: average high 77 °F, low 53 °F 77°53° SepOctober: average high 65 °F, low 41 °F 65°41° OctNovember: average high 53 °F, low 32 °F 53°32° NovDecember: average high 42 °F, low 25 °F 42°25° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.55 in precipitation 3.5 JanFebruary: 2.87 in precipitation 2.9 FebMarch: 4.04 in precipitation 4.0 MarApril: 4.09 in precipitation 4.1 AprMay: 4.70 in precipitation 4.7 MayJune: 4.26 in precipitation 4.3 JunJuly: 4.16 in precipitation 4.2 JulAugust: 4.04 in precipitation 4.0 AugSeptember: 5.36 in precipitation 5.4 SepOctober: 3.99 in precipitation 4.0 OctNovember: 3.30 in precipitation 3.3 NovDecember: 3.61 in precipitation 3.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Cashtown 1s, PA (8 mi away); precipitation: Fairfield 1.0 Nne, PA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

172147a
Blue Ridge Summit, PA · 5 mi
217277a
Emmitsburg, MD · 6 mi
173437a
Mc Knightstown, PA · 7 mi
217197a
Cascade, MD · 8 mi
173537a
Orrtanna, PA · 8 mi
217807a
Sabillasville, MD · 8 mi
173107a
Cashtown, PA · 8 mi
172617a
South Mountain, PA · 9 mi

Pennsylvania planting zones →

Questions about 17320

What planting zone is ZIP code 17320?

ZIP code 17320 (Fairfield, PA) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Fairfield, PA?

The median last spring frost (32 °F) near 17320 is April 28; after May 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cashtown 1s station.

When is the first frost in Fairfield, PA?

The median first fall frost near 17320 is October 17, giving a median frost-free growing season of 170 days.

When should I plant tomatoes in 17320?

Start tomato seeds indoors around Mar 3 – Mar 17 and set transplants outside around May 5 – May 19, one to three weeks after the median last frost.

How much rain and snow does 17320 get?

About 48 inches of precipitation a year (NOAA 1991–2020 normals, Fairfield 1.0 Nne station).

How hot do summers get in Fairfield, PA?

The average high peaks at 85 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 17320 have?

The USDA soil survey maps Hatboro at the center of ZIP 17320: silt loam, poorly drained, pH about 5.9 (moderately acidic).

Did spring come early in Fairfield, PA in 2026?

Spring leaf-out near 17320 came on Mar 20 in 2026, 6 days earlier than the 1991–2020 average (Mar 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fairfield, PA?

Intermediate onions: the longest day near 17320 is 14 h 59 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 17320 change?

Yes. The 2012 USDA map put 17320 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.