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

Planting zone for 18842 — South Gibson, PA

ZIP code 18842 (South Gibson, Susquehanna County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 14 and the first fall frost October 1.

Where ZIP 18842 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 14
First frostOct 1
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 South Gibson, 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 South Gibson, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 14median — 50% chance of a later frost
Safe for tender plantsMay 29only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 21
Growing season140 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 3 and returns around October 12.

From the NOAA station Pleasant Mt 1 W, PA — 9 miles away, elevation 1,801 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 18842

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 2 – Apr 16
SpinachSow outdoors · Apr 2 – Apr 23
Broccoli, cabbageStart indoors · Mar 5 – Mar 19
Broccoli, cabbageTransplant · Apr 23 – May 7
Onion setsPlant outdoors · Apr 16 – Apr 30
PotatoesPlant outdoors · Apr 23 – May 7
LettuceSow outdoors · Apr 16 – Apr 30
Carrots, beetsSow outdoors · Apr 23 – May 7
TomatoesStart indoors · Mar 19 – Apr 2
TomatoesTransplant · May 21 – Jun 4
Peppers, eggplantStart indoors · Mar 5 – Mar 19
Peppers, eggplantTransplant · May 28 – Jun 11
BeansSow outdoors · May 21 – Jun 4
Sweet cornSow outdoors · May 21 – Jun 4
Cucumbers, squashSow outdoors · May 21 – Jun 4
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 14) and first fall frost (Oct 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 18842 came on Apr 9 — 4 days earlier than the 1991–2020 average (Apr 13).

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 South Gibson, PA.

Soil in South Gibson, PA

The soil mapped at the center of ZIP 18842 is Mardin — channery silt loam, moderately well drained.

TextureChannery silt loama good balance for most vegetables
pH6.6neutral; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter10%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Mardin channery silt loam, 8 to 25 percent slopes, very stony.

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 18842; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South Gibson, PA

Summer high77 °Faverage high, July
Winter low12 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights169nights a year at 32 °F or less
Growing degree days1,887base 50 °F — the season’s usable heat
Longest day15 h 13 mindaylight on June 21
Shortest day9 h 08 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation51.4 inper year, rain and melted snow
Snowfall69 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 29 °F, low 12 °F 29°12° JanFebruary: average high 32 °F, low 13 °F 32°13° FebMarch: average high 40 °F, low 20 °F 40°20° MarApril: average high 53 °F, low 31 °F 53°31° AprMay: average high 65 °F, low 43 °F 65°43° MayJune: average high 73 °F, low 52 °F 73°52° JunJuly: average high 77 °F, low 56 °F 77°56° JulAugust: average high 76 °F, low 55 °F 76°55° AugSeptember: average high 69 °F, low 47 °F 69°47° SepOctober: average high 57 °F, low 36 °F 57°36° OctNovember: average high 45 °F, low 27 °F 45°27° NovDecember: average high 34 °F, low 19 °F 34°19° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.50 in precipitation, 17.3 in snowfall 3.5❄17 JanFebruary: 3.02 in precipitation, 17.7 in snowfall 3.0❄18 FebMarch: 3.57 in precipitation, 13 in snowfall 3.6❄13 MarApril: 4.22 in precipitation, 1.3 in snowfall 4.2❄1 AprMay: 4.91 in precipitation 4.9 MayJune: 4.96 in precipitation 5.0 JunJuly: 5.01 in precipitation 5.0 JulAugust: 4.50 in precipitation 4.5 AugSeptember: 4.98 in precipitation 5.0 SepOctober: 4.97 in precipitation, 0.4 in snowfall 5.0 OctNovember: 3.83 in precipitation, 4.9 in snowfall 3.8❄5 NovDecember: 3.97 in precipitation, 14.6 in snowfall 4.0❄15 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Pleasant Mt 1 W, PA (9 mi away); precipitation: Pleasant Mt 1 W, PA (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

4 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

188206a
Gibson, PA · 2 mi
188255b
Jackson, PA · 4 mi
188236a
Harford, PA · 4 mi
184705b
Union Dale, PA · 5 mi
188266a
Kingsley, PA · 6 mi
184655b
Thompson, PA · 7 mi
188345b
New Milford, PA · 7 mi
184416a
Lenoxville, PA · 7 mi

Pennsylvania planting zones →

Questions about 18842

What planting zone is ZIP code 18842?

ZIP code 18842 (South Gibson, 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 South Gibson, PA?

The median last spring frost (32 °F) near 18842 is May 14; after May 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Pleasant Mt 1 W station.

When is the first frost in South Gibson, PA?

The median first fall frost near 18842 is October 1, giving a median frost-free growing season of 140 days.

When should I plant tomatoes in 18842?

Start tomato seeds indoors around Mar 19 – Apr 2 and set transplants outside around May 21 – Jun 4, one to three weeks after the median last frost.

How much rain and snow does 18842 get?

About 51.4 inches of precipitation a year and 69 inches of snowfall (NOAA 1991–2020 normals, Pleasant Mt 1 W station).

How hot do summers get in South Gibson, PA?

The average high peaks at 77 °F in July, with about 1 days a year at 90 °F or more.

What kind of soil does 18842 have?

The USDA soil survey maps Mardin at the center of ZIP 18842: channery silt loam, moderately well drained, pH about 6.6 (neutral).

Did spring come early in South Gibson, PA in 2026?

Spring leaf-out near 18842 came on Apr 9 in 2026, 4 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in South Gibson, PA?

Long-day onions: the longest day near 18842 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 18842 change?

Yes. The 2012 USDA map put 18842 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.