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

Planting zone for 15557 — Rockwood, PA

ZIP code 15557 (Rockwood, Somerset County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 2 and the first fall frost October 17.

Where ZIP 15557 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 frostMay 2
First frostOct 17
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Rockwood, 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 Rockwood, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 2median — 50% chance of a later frost
Safe for tender plantsMay 18only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 5
Growing season168 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 28.

From the NOAA station Hidden Valley, PA — 9 miles away, elevation 2,877 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 15557

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 21 – Apr 4
SpinachSow outdoors · Mar 21 – Apr 11
Broccoli, cabbageStart indoors · Feb 21 – Mar 7
Broccoli, cabbageTransplant · Apr 11 – Apr 25
Onion setsPlant outdoors · Apr 4 – Apr 18
PotatoesPlant outdoors · Apr 11 – Apr 25
LettuceSow outdoors · Apr 4 – Apr 18
Carrots, beetsSow outdoors · Apr 11 – Apr 25
TomatoesStart indoors · Mar 7 – Mar 21
TomatoesTransplant · May 9 – May 23
Peppers, eggplantStart indoors · Feb 21 – Mar 7
Peppers, eggplantTransplant · May 16 – May 30
BeansSow outdoors · May 9 – May 23
Sweet cornSow outdoors · May 9 – May 23
Cucumbers, squashSow outdoors · May 9 – May 23
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 (May 2) 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 15557 came on Mar 15 — 22 days earlier than the 1991–2020 average (Apr 6).

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 Rockwood, PA.

Soil in Rockwood, PA

The soil mapped at the center of ZIP 15557 is Wharton — slightly decomposed plant material, moderately well drained.

TextureSlightly decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter69%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Wharton 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 15557; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Rockwood, PA

Summer high77 °Faverage high, July
Winter low17 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights142nights a year at 32 °F or less
Growing degree days2,301base 50 °F — the season’s usable heat
Longest day15 h 00 mindaylight on June 21
Shortest day9 h 20 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation47.1 inper year, rain and melted snow
Snowfall96 inper year; 70 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 32 °F, low 17 °F 32°17° JanFebruary: average high 35 °F, low 18 °F 35°18° FebMarch: average high 44 °F, low 25 °F 44°25° MarApril: average high 57 °F, low 34 °F 57°34° AprMay: average high 67 °F, low 47 °F 67°47° MayJune: average high 72 °F, low 56 °F 72°56° JunJuly: average high 77 °F, low 61 °F 77°61° JulAugust: average high 75 °F, low 59 °F 75°59° AugSeptember: average high 70 °F, low 52 °F 70°52° SepOctober: average high 59 °F, low 40 °F 59°40° OctNovember: average high 47 °F, low 30 °F 47°30° NovDecember: average high 37 °F, low 23 °F 37°23° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.74 in precipitation, 27.6 in snowfall 3.7❄28 JanFebruary: 3.31 in precipitation, 23.6 in snowfall 3.3❄24 FebMarch: 4.12 in precipitation, 15.4 in snowfall 4.1❄15 MarApril: 4.22 in precipitation, 3.1 in snowfall 4.2❄3 AprMay: 4.83 in precipitation 4.8 MayJune: 4.27 in precipitation 4.3 JunJuly: 4.02 in precipitation 4.0 JulAugust: 3.88 in precipitation 3.9 AugSeptember: 3.96 in precipitation 4.0 SepOctober: 3.37 in precipitation, 0.9 in snowfall 3.4❄1 OctNovember: 3.41 in precipitation, 5.9 in snowfall 3.4❄6 NovDecember: 3.93 in precipitation, 19.7 in snowfall 3.9❄20 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hidden Valley, PA (9 mi away); precipitation: Somerset, PA (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

155516a
Markleton, PA · 5 mi
155426a
Garrett, PA · 8 mi
155026a
Hidden Valley, PA · 8 mi
155406a
Fort Hill, PA · 8 mi
155106a
Somerset, PA · 9 mi
155016a
Somerset, PA · 9 mi
154856a
Ursina, PA · 10 mi
154246a
Confluence, PA · 10 mi

Pennsylvania planting zones →

Questions about 15557

What planting zone is ZIP code 15557?

ZIP code 15557 (Rockwood, 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 Rockwood, PA?

The median last spring frost (32 °F) near 15557 is May 2; after May 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hidden Valley station.

When is the first frost in Rockwood, PA?

The median first fall frost near 15557 is October 17, giving a median frost-free growing season of 168 days.

When should I plant tomatoes in 15557?

Start tomato seeds indoors around Mar 7 – Mar 21 and set transplants outside around May 9 – May 23, one to three weeks after the median last frost.

How much rain and snow does 15557 get?

About 47.1 inches of precipitation a year and 96 inches of snowfall (NOAA 1991–2020 normals, Somerset station).

How hot do summers get in Rockwood, PA?

The average high peaks at 77 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 15557 have?

The USDA soil survey maps Wharton at the center of ZIP 15557: slightly decomposed plant material, moderately well drained, pH about 5.0 (strongly acidic).

Did spring come early in Rockwood, PA in 2026?

Spring leaf-out near 15557 came on Mar 15 in 2026, 22 days earlier than the 1991–2020 average (Apr 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Rockwood, PA?

Long-day onions: the longest day near 15557 is 15 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 15557 change?

Yes. The 2012 USDA map put 15557 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.