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

Planting zone for 16159 — West Middlesex, PA

ZIP code 16159 (West Middlesex, Mercer County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 30 and the first fall frost October 23.

Where ZIP 16159 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostApr 30
First frostOct 23
2012 zone6a

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for West Middlesex, 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 West Middlesex, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 30median — 50% chance of a later frost
Safe for tender plantsMay 19only 10% chance of frost after
First fall frostOctober 23median — 10% chance by Oct 6
Growing season175 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 20 and returns around November 2.

From the NOAA station New Castle 1 N, PA — 11 miles away, elevation 827 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 16159

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 19 – Apr 2
SpinachSow outdoors · Mar 19 – Apr 9
Broccoli, cabbageStart indoors · Feb 19 – Mar 5
Broccoli, cabbageTransplant · Apr 9 – Apr 23
Onion setsPlant outdoors · Apr 2 – Apr 16
PotatoesPlant outdoors · Apr 9 – Apr 23
LettuceSow outdoors · Apr 2 – Apr 16
Carrots, beetsSow outdoors · Apr 9 – Apr 23
TomatoesStart indoors · Mar 5 – Mar 19
TomatoesTransplant · May 7 – May 21
Peppers, eggplantStart indoors · Feb 19 – Mar 5
Peppers, eggplantTransplant · May 14 – May 28
BeansSow outdoors · May 7 – May 21
Sweet cornSow outdoors · May 7 – May 21
Cucumbers, squashSow outdoors · May 7 – May 21
Fall lettuce, spinachSow outdoors · Aug 28 – Sep 11
GarlicPlant cloves · Oct 9 – Nov 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 30) and first fall frost (Oct 23) 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 16159 came on Mar 16 — 18 days earlier than the 1991–2020 average (Apr 3).

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 6a in Pennsylvania

598 plants native to the lower 48 states, recorded in Pennsylvania, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 76

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 121

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 207

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 170

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 9

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 West Middlesex, PA.

Soil in West Middlesex, PA

The soil mapped at the center of ZIP 16159 is Canfield — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.3slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter3.3%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Canfield silt loam, 0 to 3 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 16159; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in West Middlesex, PA

Summer high86 °Faverage high, July
Winter low19 °Faverage low, January
Hot days21days a year at 90 °F or more
Freezing nights134nights a year at 32 °F or less
Growing degree days3,088base 50 °F — the season’s usable heat
Longest day15 h 09 mindaylight on June 21
Shortest day9 h 12 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation41.8 inper year, rain and melted snow
Snowfall28 inper year; 42 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 19 °F 37°19° JanFebruary: average high 40 °F, low 20 °F 40°20° FebMarch: average high 49 °F, low 27 °F 49°27° MarApril: average high 63 °F, low 36 °F 63°36° AprMay: average high 73 °F, low 47 °F 73°47° MayJune: average high 82 °F, low 56 °F 82°56° JunJuly: average high 86 °F, low 60 °F 86°60° JulAugust: average high 85 °F, low 59 °F 85°59° AugSeptember: average high 79 °F, low 52 °F 79°52° SepOctober: average high 66 °F, low 41 °F 66°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 · ❄ = snowfall

0″1″2″3″4″5″January: 2.86 in precipitation, 10.1 in snowfall 2.9❄10 JanFebruary: 2.20 in precipitation, 7.7 in snowfall 2.2❄8 FebMarch: 3.08 in precipitation, 3.7 in snowfall 3.1❄4 MarApril: 3.65 in precipitation, 0.3 in snowfall 3.6 AprMay: 3.89 in precipitation 3.9 MayJune: 4.47 in precipitation 4.5 JunJuly: 4.55 in precipitation 4.5 JulAugust: 3.91 in precipitation 3.9 AugSeptember: 3.86 in precipitation 3.9 SepOctober: 3.22 in precipitation 3.2 OctNovember: 2.96 in precipitation, 0.8 in snowfall 3.0❄1 NovDecember: 3.13 in precipitation, 4.9 in snowfall 3.1❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: New Castle 1 N, PA (11 mi away); precipitation: New Castle 1 N, PA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

161616a
Wheatland, PA · 3 mi
161436a
Pulaski, PA · 4 mi
161216a
Farrell, PA · 4 mi
161406a
New Bedford, PA · 5 mi
444256a
Hubbard, OH · 5 mi
161466a
Sharon, PA · 6 mi
161486a
Hermitage, PA · 6 mi
161556a
Villa Maria, PA · 6 mi

Pennsylvania planting zones →

Questions about 16159

What planting zone is ZIP code 16159?

ZIP code 16159 (West Middlesex, PA) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in West Middlesex, PA?

The median last spring frost (32 °F) near 16159 is April 30; after May 19 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, New Castle 1 N station.

When is the first frost in West Middlesex, PA?

The median first fall frost near 16159 is October 23, giving a median frost-free growing season of 175 days.

When should I plant tomatoes in 16159?

Start tomato seeds indoors around Mar 5 – Mar 19 and set transplants outside around May 7 – May 21, one to three weeks after the median last frost.

How much rain and snow does 16159 get?

About 41.8 inches of precipitation a year and 28 inches of snowfall (NOAA 1991–2020 normals, New Castle 1 N station).

How hot do summers get in West Middlesex, PA?

The average high peaks at 86 °F in July, with about 21 days a year at 90 °F or more.

What kind of soil does 16159 have?

The USDA soil survey maps Canfield at the center of ZIP 16159: silt loam, moderately well drained, pH about 6.3 (slightly acidic).

Did spring come early in West Middlesex, PA in 2026?

Spring leaf-out near 16159 came on Mar 16 in 2026, 18 days earlier than the 1991–2020 average (Apr 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in West Middlesex, PA?

Long-day onions: the longest day near 16159 is 15 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).