Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 17851 — Mount Carmel, PA

ZIP code 17851 (Mount Carmel, Northumberland County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 27 and the first fall frost October 20.

Where ZIP 17851 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 27

First frostOct 20

2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Carmel, 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 Mount Carmel, PA

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 27median — 50% chance of a later frost

Safe for tender plantsMay 15only 10% chance of frost after

First fall frostOctober 20median — 10% chance by Oct 4

Growing season172 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 13 and returns around November 2.

From the NOAA station Bear Gap, PA — 4 miles away, elevation 1,014 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 17851

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 16 – Mar 30

SpinachSow outdoors · Mar 16 – Apr 6

Broccoli, cabbageStart indoors · Feb 16 – Mar 2

Broccoli, cabbageTransplant · Apr 6 – Apr 20

Onion setsPlant outdoors · Mar 30 – Apr 13

PotatoesPlant outdoors · Apr 6 – Apr 20

LettuceSow outdoors · Mar 30 – Apr 13

Carrots, beetsSow outdoors · Apr 6 – Apr 20

TomatoesStart indoors · Mar 2 – Mar 16

TomatoesTransplant · May 4 – May 18

Peppers, eggplantStart indoors · Feb 16 – Mar 2

Peppers, eggplantTransplant · May 11 – May 25

BeansSow outdoors · May 4 – May 18

Sweet cornSow outdoors · May 4 – May 18

Cucumbers, squashSow outdoors · May 4 – May 18

Fall lettuce, spinachSow outdoors · Aug 25 – Sep 8

GarlicPlant cloves · Oct 6 – Nov 10

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 20) 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 17851 came on Apr 1 — 9 days earlier than the 1991–2020 average (Apr 10).

average
Apr 102026
Apr 1

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 6b in Pennsylvania

605 plants native to the lower 48 states, recorded in Pennsylvania, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

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 Mount Carmel, PA.

Soil in Mount Carmel, PA

The center of ZIP 17851 is mapped as Udorthents, sandstone and shale: built-over ground without natural soil data. Garden soil here is usually imported or disturbed — test before you plant.

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 17851; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Carmel, PA

Summer high84 °Faverage high, July

Winter low19 °Faverage low, January

Hot days10days a year at 90 °F or more

Freezing nights127nights a year at 32 °F or less

Growing degree days2,888base 50 °F — the season’s usable heat

Longest day15 h 06 mindaylight on June 21

Shortest day9 h 14 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation48 inper year, rain and melted snow

Snowfall34 inper year; 40 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

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

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

178326b

Marion Heights, PA · 2 mi

178406b

Locust Gap, PA · 2 mi

Locustdale, PA · 3 mi

Pennsylvania planting zones →

Questions about 17851

What planting zone is ZIP code 17851?

ZIP code 17851 (Mount Carmel, 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 Mount Carmel, PA?

The median last spring frost (32 °F) near 17851 is April 27; after May 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bear Gap station.

When is the first frost in Mount Carmel, PA?

The median first fall frost near 17851 is October 20, giving a median frost-free growing season of 172 days.

When should I plant tomatoes in 17851?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 17851 get?

About 48 inches of precipitation a year and 34 inches of snowfall (NOAA 1991–2020 normals, Bear Gap station).

How hot do summers get in Mount Carmel, PA?

The average high peaks at 84 °F in July, with about 10 days a year at 90 °F or more.

Did spring come early in Mount Carmel, PA in 2026?

Spring leaf-out near 17851 came on Apr 1 in 2026, 9 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Carmel, PA?

Long-day onions: the longest day near 17851 is 15 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 17851 change?

Yes. The 2012 USDA map put 17851 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.