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

Planting zone for 15423 — Coal Center, PA

ZIP code 15423 (Coal Center, Washington County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 13 and the first fall frost November 5.

Where ZIP 15423 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostApr 13
First frostNov 5
2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Coal Center, 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 Coal Center, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 13median — 50% chance of a later frost
Safe for tender plantsMay 5only 10% chance of frost after
First fall frostNovember 5median — 10% chance by Oct 25
Growing season205 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 31 and returns around November 16.

From the NOAA station Charleroi Lock 4, PA — 4 miles away, elevation 748 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 15423

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 2 – Mar 16
SpinachSow outdoors · Mar 2 – Mar 23
Broccoli, cabbageStart indoors · Feb 2 – Feb 16
Broccoli, cabbageTransplant · Mar 23 – Apr 6
Onion setsPlant outdoors · Mar 16 – Mar 30
PotatoesPlant outdoors · Mar 23 – Apr 6
LettuceSow outdoors · Mar 16 – Mar 30
Carrots, beetsSow outdoors · Mar 23 – Apr 6
TomatoesStart indoors · Feb 16 – Mar 2
TomatoesTransplant · Apr 20 – May 4
Peppers, eggplantStart indoors · Feb 2 – Feb 16
Peppers, eggplantTransplant · Apr 27 – May 11
BeansSow outdoors · Apr 20 – May 4
Sweet cornSow outdoors · Apr 20 – May 4
Cucumbers, squashSow outdoors · Apr 20 – May 4
Fall lettuce, spinachSow outdoors · Sep 10 – Sep 24
GarlicPlant cloves · Oct 22 – Nov 26
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 13) and first fall frost (Nov 5) 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 15423 came on Mar 10 — 15 days earlier than the 1991–2020 average (Mar 25).

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).

Soil in Coal Center, PA

The soil mapped at the center of ZIP 15423 is Culleoka — channery silt loam, well drained.

TextureChannery silt loama good balance for most vegetables
pH6.3slightly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Culleoka channery silt loam, 15 to 25 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 15423; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Coal Center, PA

Summer high85 °Faverage high, July
Winter low21 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights108nights a year at 32 °F or less
Growing degree days3,400base 50 °F — the season’s usable heat
Longest day15 h 02 mindaylight on June 21
Shortest day9 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.9 inper year, rain and melted snow
Snowfall10 inper year; 11 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 39 °F, low 21 °F 39°21° JanFebruary: average high 42 °F, low 22 °F 42°22° FebMarch: average high 51 °F, low 29 °F 51°29° MarApril: average high 64 °F, low 39 °F 64°39° AprMay: average high 74 °F, low 51 °F 74°51° MayJune: average high 81 °F, low 60 °F 81°60° JunJuly: average high 85 °F, low 64 °F 85°64° JulAugust: average high 84 °F, low 63 °F 84°63° AugSeptember: average high 78 °F, low 56 °F 78°56° SepOctober: average high 66 °F, low 44 °F 66°44° OctNovember: average high 54 °F, low 34 °F 54°34° NovDecember: average high 43 °F, low 27 °F 43°27° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.24 in precipitation, 3.8 in snowfall 3.2❄4 JanFebruary: 2.75 in precipitation, 2.7 in snowfall 2.8❄3 FebMarch: 3.42 in precipitation, 2.1 in snowfall 3.4❄2 MarApril: 3.45 in precipitation 3.5 AprMay: 3.94 in precipitation 3.9 MayJune: 4.33 in precipitation 4.3 JunJuly: 4.05 in precipitation 4.0 JulAugust: 3.50 in precipitation 3.5 AugSeptember: 3.26 in precipitation 3.3 SepOctober: 2.86 in precipitation 2.9 OctNovember: 2.85 in precipitation, 0.2 in snowfall 2.9 NovDecember: 3.27 in precipitation, 1.5 in snowfall 3.3❄2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Charleroi Lock 4, PA (4 mi away); precipitation: Charleroi Lock 4, PA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

154346b
Elco, PA · 2 mi
150226b
Charleroi, PA · 2 mi
154666b
Newell, PA · 2 mi
154276b
Daisytown, PA · 3 mi
154196b
California, PA · 3 mi
154326b
Dunlevy, PA · 4 mi
154386b
Fayette City, PA · 4 mi
154126b
Allenport, PA · 4 mi

Pennsylvania planting zones →

Questions about 15423

What planting zone is ZIP code 15423?

ZIP code 15423 (Coal Center, PA) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Coal Center, PA?

The median last spring frost (32 °F) near 15423 is April 13; after May 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Charleroi Lock 4 station.

When is the first frost in Coal Center, PA?

The median first fall frost near 15423 is November 5, giving a median frost-free growing season of 205 days.

When should I plant tomatoes in 15423?

Start tomato seeds indoors around Feb 16 – Mar 2 and set transplants outside around Apr 20 – May 4, one to three weeks after the median last frost.

How much rain and snow does 15423 get?

About 40.9 inches of precipitation a year and 10 inches of snowfall (NOAA 1991–2020 normals, Charleroi Lock 4 station).

How hot do summers get in Coal Center, 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 15423 have?

The USDA soil survey maps Culleoka at the center of ZIP 15423: channery silt loam, well drained, pH about 6.3 (slightly acidic).

Did spring come early in Coal Center, PA in 2026?

Spring leaf-out near 15423 came on Mar 10 in 2026, 15 days earlier than the 1991–2020 average (Mar 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Coal Center, PA?

Long-day onions: the longest day near 15423 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).