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

Planting zone for 18631 — Mifflinville, PA

ZIP code 18631 (Mifflinville, Columbia County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 4 and the first fall frost October 11.

Where ZIP 18631 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 frostMay 4
First frostOct 11
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 Mifflinville, 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 Mifflinville, PA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 4median — 50% chance of a later frost
Safe for tender plantsMay 19only 10% chance of frost after
First fall frostOctober 11median — 10% chance by Sep 29
Growing season159 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 24.

From the NOAA station Benton 3 Ne, PA — 14 miles away, elevation 1,096 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 18631

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 23 – Apr 6
SpinachSow outdoors · Mar 23 – Apr 13
Broccoli, cabbageStart indoors · Feb 23 – Mar 9
Broccoli, cabbageTransplant · Apr 13 – Apr 27
Onion setsPlant outdoors · Apr 6 – Apr 20
PotatoesPlant outdoors · Apr 13 – Apr 27
LettuceSow outdoors · Apr 6 – Apr 20
Carrots, beetsSow outdoors · Apr 13 – Apr 27
TomatoesStart indoors · Mar 9 – Mar 23
TomatoesTransplant · May 11 – May 25
Peppers, eggplantStart indoors · Feb 23 – Mar 9
Peppers, eggplantTransplant · May 18 – Jun 1
BeansSow outdoors · May 11 – May 25
Sweet cornSow outdoors · May 11 – May 25
Cucumbers, squashSow outdoors · May 11 – May 25
Fall lettuce, spinachSow outdoors · Aug 16 – Aug 30
GarlicPlant cloves · Sep 27 – Nov 1
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 4) and first fall frost (Oct 11) 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 18631 came on Mar 31 — 4 days earlier than the 1991–2020 average (Apr 4).

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.

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 122

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 209

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 173

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °F

Vines 10

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 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °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 Mifflinville, PA.

Soil in Mifflinville, PA

The soil mapped at the center of ZIP 18631 is Chenango — gravelly sandy loam, well drained.

TextureGravelly sandy loamdrains and warms fast; dries out and needs more feeding
pH5.3strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4%moderate
Hydrologic groupAwater soaks in fast
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Chenango gravelly sandy loam, 12 to 20 percent slopes, moderately eroded.

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 18631; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mifflinville, PA

Summer high80 °Faverage high, July
Winter low16 °Faverage low, January
Hot days4days a year at 90 °F or more
Freezing nights145nights a year at 32 °F or less
Growing degree days2,377base 50 °F — the season’s usable heat
Longest day15 h 08 mindaylight on June 21
Shortest day9 h 13 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation47.5 inper year, rain and melted snow
Snowfall36 inper year; 52 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 33 °F, low 16 °F 33°16° JanFebruary: average high 36 °F, low 18 °F 36°18° FebMarch: average high 44 °F, low 25 °F 44°25° MarApril: average high 58 °F, low 35 °F 58°35° AprMay: average high 69 °F, low 46 °F 69°46° MayJune: average high 76 °F, low 55 °F 76°55° JunJuly: average high 80 °F, low 58 °F 80°58° JulAugust: average high 78 °F, low 57 °F 78°57° AugSeptember: average high 72 °F, low 50 °F 72°50° SepOctober: average high 60 °F, low 39 °F 60°39° OctNovember: average high 48 °F, low 31 °F 48°31° NovDecember: average high 38 °F, low 22 °F 38°22° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.40 in precipitation, 10.7 in snowfall 3.4❄11 JanFebruary: 2.57 in precipitation, 10.2 in snowfall 2.6❄10 FebMarch: 3.44 in precipitation, 6 in snowfall 3.4❄6 MarApril: 4.20 in precipitation, 0.8 in snowfall 4.2❄1 AprMay: 4.34 in precipitation 4.3 MayJune: 4.70 in precipitation 4.7 JunJuly: 4.52 in precipitation 4.5 JulAugust: 4.43 in precipitation 4.4 AugSeptember: 4.58 in precipitation 4.6 SepOctober: 4.35 in precipitation, 0.2 in snowfall 4.3 OctNovember: 3.18 in precipitation, 1.1 in snowfall 3.2❄1 NovDecember: 3.75 in precipitation, 6.6 in snowfall 3.8❄7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Benton 3 Ne, PA (14 mi away); precipitation: Shickshinny 3 N, PA (13 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

186036b
Berwick, PA · 5 mi
186356b
Nescopeck, PA · 5 mi
178156b
Bloomsburg, PA · 7 mi
186016b
Beach Haven, PA · 7 mi
182466b
Rock Glen, PA · 8 mi
178596b
Orangeville, PA · 8 mi
179856b
Zion Grove, PA · 8 mi
182416b
Nuremberg, PA · 9 mi

Pennsylvania planting zones →

Questions about 18631

What planting zone is ZIP code 18631?

ZIP code 18631 (Mifflinville, 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 Mifflinville, PA?

The median last spring frost (32 °F) near 18631 is May 4; after May 19 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Benton 3 Ne station.

When is the first frost in Mifflinville, PA?

The median first fall frost near 18631 is October 11, giving a median frost-free growing season of 159 days.

When should I plant tomatoes in 18631?

Start tomato seeds indoors around Mar 9 – Mar 23 and set transplants outside around May 11 – May 25, one to three weeks after the median last frost.

How much rain and snow does 18631 get?

About 47.5 inches of precipitation a year and 36 inches of snowfall (NOAA 1991–2020 normals, Shickshinny 3 N station).

How hot do summers get in Mifflinville, PA?

The average high peaks at 80 °F in July, with about 4 days a year at 90 °F or more.

What kind of soil does 18631 have?

The USDA soil survey maps Chenango at the center of ZIP 18631: gravelly sandy loam, well drained, pH about 5.3 (strongly acidic).

Did spring come early in Mifflinville, PA in 2026?

Spring leaf-out near 18631 came on Mar 31 in 2026, 4 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mifflinville, PA?

Long-day onions: the longest day near 18631 is 15 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).