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

Planting zone for 17055 — Mechanicsburg, PA

ZIP code 17055 (Mechanicsburg, Cumberland County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 9 and the first fall frost November 1.

Where ZIP 17055 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 9
First frostNov 1
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 Mechanicsburg, 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 Mechanicsburg, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 9median — 50% chance of a later frost
Safe for tender plantsApril 25only 10% chance of frost after
First fall frostNovember 1median — 10% chance by Oct 16
Growing season205 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 29 and returns around November 12.

From the NOAA station Harrisburg Cptl Cy Airport, PA — 8 miles away, elevation 341 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 17055

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 26 – Mar 12
SpinachSow outdoors · Feb 26 – Mar 19
Broccoli, cabbageStart indoors · Jan 29 – Feb 12
Broccoli, cabbageTransplant · Mar 19 – Apr 2
Onion setsPlant outdoors · Mar 12 – Mar 26
PotatoesPlant outdoors · Mar 19 – Apr 2
LettuceSow outdoors · Mar 12 – Mar 26
Carrots, beetsSow outdoors · Mar 19 – Apr 2
TomatoesStart indoors · Feb 12 – Feb 26
TomatoesTransplant · Apr 16 – Apr 30
Peppers, eggplantStart indoors · Jan 29 – Feb 12
Peppers, eggplantTransplant · Apr 23 – May 7
BeansSow outdoors · Apr 16 – Apr 30
Sweet cornSow outdoors · Apr 16 – Apr 30
Cucumbers, squashSow outdoors · Apr 16 – Apr 30
Fall lettuce, spinachSow outdoors · Sep 6 – Sep 20
GarlicPlant cloves · Oct 18 – Nov 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 9) and first fall frost (Nov 1) 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 17055 came on Mar 21 — 8 days earlier than the 1991–2020 average (Mar 29).

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 Mechanicsburg, PA.

Soil in Mechanicsburg, PA

The soil mapped at the center of ZIP 17055 is Duffield — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupBwater soaks in moderately
Farmland classprime farmlandUSDA classification

Map unit: Duffield silt loam, 3 to 8 percent slopes.

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 17055; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mechanicsburg, PA

Summer high88 °Faverage high, July
Winter low25 °Faverage low, January
Hot days26days a year at 90 °F or more
Freezing nights102nights a year at 32 °F or less
Growing degree days3,840base 50 °F — the season’s usable heat
Longest day15 h 02 mindaylight on June 21
Shortest day9 h 18 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation45.6 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 40 °F, low 25 °F 40°25° JanFebruary: average high 43 °F, low 26 °F 43°26° FebMarch: average high 53 °F, low 34 °F 53°34° MarApril: average high 65 °F, low 43 °F 65°43° AprMay: average high 75 °F, low 53 °F 75°53° MayJune: average high 83 °F, low 63 °F 83°63° JunJuly: average high 88 °F, low 67 °F 88°67° JulAugust: average high 85 °F, low 66 °F 85°66° AugSeptember: average high 79 °F, low 58 °F 79°58° SepOctober: average high 67 °F, low 47 °F 67°47° OctNovember: average high 55 °F, low 37 °F 55°37° NovDecember: average high 44 °F, low 30 °F 44°30° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.07 in precipitation 3.1 JanFebruary: 2.72 in precipitation 2.7 FebMarch: 3.73 in precipitation 3.7 MarApril: 3.65 in precipitation 3.6 AprMay: 4.00 in precipitation 4.0 MayJune: 4.43 in precipitation 4.4 JunJuly: 4.58 in precipitation 4.6 JulAugust: 3.84 in precipitation 3.8 AugSeptember: 4.90 in precipitation 4.9 SepOctober: 3.84 in precipitation 3.8 OctNovember: 3.16 in precipitation 3.2 NovDecember: 3.69 in precipitation 3.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Harrisburg Cptl Cy Airport, PA (8 mi away); precipitation: Mechanicsburg 1.0 Nnw, PA (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

170277a
Grantham, PA · 2 mi
170017a
Camp Hill, PA · 5 mi
170507a
Mechanicsburg, PA · 5 mi
170117a
Camp Hill, PA · 5 mi
170727a
New Kingstown, PA · 6 mi
170197a
Dillsburg, PA · 6 mi
170077a
Boiling Springs, PA · 7 mi
170437a
Lemoyne, PA · 7 mi

All 2 ZIP codes in Mechanicsburg → · Pennsylvania planting zones →

Questions about 17055

What planting zone is ZIP code 17055?

ZIP code 17055 (Mechanicsburg, 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 Mechanicsburg, PA?

The median last spring frost (32 °F) near 17055 is April 9; after April 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Harrisburg Cptl Cy Airport station.

When is the first frost in Mechanicsburg, PA?

The median first fall frost near 17055 is November 1, giving a median frost-free growing season of 205 days.

When should I plant tomatoes in 17055?

Start tomato seeds indoors around Feb 12 – Feb 26 and set transplants outside around Apr 16 – Apr 30, one to three weeks after the median last frost.

How much rain and snow does 17055 get?

About 45.6 inches of precipitation a year (NOAA 1991–2020 normals, Mechanicsburg 1.0 Nnw station).

How hot do summers get in Mechanicsburg, PA?

The average high peaks at 88 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 17055 have?

The USDA soil survey maps Duffield at the center of ZIP 17055: silt loam, well drained, pH about 6.7 (neutral).

Did spring come early in Mechanicsburg, PA in 2026?

Spring leaf-out near 17055 came on Mar 21 in 2026, 8 days earlier than the 1991–2020 average (Mar 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mechanicsburg, PA?

Long-day onions: the longest day near 17055 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 17055 change?

Yes. The 2012 USDA map put 17055 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.