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

Planting zone for 18928 — Holicong, PA

ZIP code 18928 (Holicong, Bucks County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 13 and the first fall frost October 30.

Where ZIP 18928 is

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.

Zone7a0 to 5 °F

Coldest night−17.8 to −15 °C

Last frostApr 13

First frostOct 30

2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Holicong, 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 Holicong, 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 plantsApril 27only 10% chance of frost after

First fall frostOctober 30median — 10% chance by Oct 15

Growing season198 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around November 10.

From the NOAA station Doylestown Airport, PA — 4 miles away, elevation 394 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 18928

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 4 – Sep 18

GarlicPlant cloves · Oct 16 – Nov 20

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 13) and first fall frost (Oct 30) 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 18928 came on Mar 24 — about the same time as the 1991–2020 average (Mar 26).

average
Mar 262026
Mar 24

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 7a in Pennsylvania

620 plants native to the lower 48 states, recorded in Pennsylvania, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. 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 Holicong, PA.

Soil in Holicong, PA

The soil mapped at the center of ZIP 18928 is Duffield — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.7neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupBwater soaks in moderately

Farmland classprime farmlandUSDA classification

Map unit: Duffield silt loam, 3 to 8 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 18928; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Holicong, PA

Summer high86 °Faverage high, July

Winter low23 °Faverage low, January

Hot days20days a year at 90 °F or more

Freezing nights106nights a year at 32 °F or less

Growing degree days3,410base 50 °F — the season’s usable heat

Longest day15 h 03 mindaylight on June 21

Shortest day9 h 17 mindaylight on December 21

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

Precipitation50 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Doylestown Airport, PA (4 mi away); precipitation: Furlong 0.7 Sw, PA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

189127a

Buckingham, PA · 2 mi

189387a

New Hope, PA · 3 mi

189137a

Carversville, PA · 3 mi

189027a

Doylestown, PA · 3 mi

189227a

Forest Grove, PA · 3 mi

189317a

Lahaska, PA · 3 mi

189917a

Warminster, PA · 3 mi

189637a

Solebury, PA · 4 mi

Pennsylvania planting zones →

Questions about 18928

What planting zone is ZIP code 18928?

ZIP code 18928 (Holicong, PA) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Holicong, PA?

The median last spring frost (32 °F) near 18928 is April 13; after April 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Doylestown Airport station.

When is the first frost in Holicong, PA?

The median first fall frost near 18928 is October 30, giving a median frost-free growing season of 198 days.

When should I plant tomatoes in 18928?

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 18928 get?

About 50 inches of precipitation a year (NOAA 1991–2020 normals, Furlong 0.7 Sw station).

How hot do summers get in Holicong, PA?

The average high peaks at 86 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 18928 have?

The USDA soil survey maps Duffield at the center of ZIP 18928: silt loam, well drained, pH about 6.7 (neutral).

Did spring come early in Holicong, PA in 2026?

Spring leaf-out near 18928 came on Mar 24 in 2026, about the same as the 1991–2020 average (Mar 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Holicong, PA?

Long-day onions: the longest day near 18928 is 15 h 03 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 18928 change?

Yes. The 2012 USDA map put 18928 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.