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

Planting zone for 15924 — Cairnbrook, PA

ZIP code 15924 (Cairnbrook, Somerset County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 4 and the first fall frost October 10.

Where ZIP 15924 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 4

First frostOct 10

2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cairnbrook, 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 Cairnbrook, 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 21only 10% chance of frost after

First fall frostOctober 10median — 10% chance by Sep 28

Growing season158 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 21 and returns around October 22.

From the NOAA station Shawnee Sp, PA — 8 miles away, elevation 1,276 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 15924

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 15 – Aug 29

GarlicPlant cloves · Sep 26 – Oct 31

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 4) and first fall frost (Oct 10) 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 15924 came on Mar 30 — 11 days earlier than the 1991–2020 average (Apr 10).

average
Apr 102026
Mar 30

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.

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 Cairnbrook, PA.

Soil in Cairnbrook, PA

The soil mapped at the center of ZIP 15924 is Hazleton — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH4.3strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter69%high

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Hazleton channery sandy loam, 3 to 8 percent slopes, extremely 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 15924; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cairnbrook, PA

Summer high84 °Faverage high, July

Winter low19 °Faverage low, January

Hot days10days a year at 90 °F or more

Freezing nights149nights a year at 32 °F or less

Growing degree days2,743base 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)

Precipitation40.3 inper year, rain and melted snow

Snowfall97 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Shawnee Sp, PA (8 mi away); precipitation: Buckstown 1 Se, PA (5 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.

155596b

Schellsburg, PA · 5 mi

159266a

Central City, PA · 6 mi

155546b

New Paris, PA · 8 mi

159366a

Hooversville, PA · 8 mi

159636a

Windber, PA · 8 mi

155396b

Fishertown, PA · 9 mi

155636a

Stoystown, PA · 9 mi

155506b

Manns Choice, PA · 9 mi

Pennsylvania planting zones →

Questions about 15924

What planting zone is ZIP code 15924?

ZIP code 15924 (Cairnbrook, 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 Cairnbrook, PA?

The median last spring frost (32 °F) near 15924 is May 4; after May 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Shawnee Sp station.

When is the first frost in Cairnbrook, PA?

The median first fall frost near 15924 is October 10, giving a median frost-free growing season of 158 days.

When should I plant tomatoes in 15924?

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 15924 get?

About 40.3 inches of precipitation a year and 97 inches of snowfall (NOAA 1991–2020 normals, Buckstown 1 Se station).

How hot do summers get in Cairnbrook, PA?

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

What kind of soil does 15924 have?

The USDA soil survey maps Hazleton at the center of ZIP 15924: slightly decomposed plant material, well drained, pH about 4.3 (strongly acidic).

Did spring come early in Cairnbrook, PA in 2026?

Spring leaf-out near 15924 came on Mar 30 in 2026, 11 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cairnbrook, PA?

Long-day onions: the longest day near 15924 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).