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

Planting zone for 17020 — Duncannon, PA

ZIP code 17020 (Duncannon, Perry County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 15 and the first fall frost October 23.

Where ZIP 17020 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.

Zone7a0 to 5 °F

Coldest night−17.8 to −15 °C

Last frostApr 15

First frostOct 23

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 Duncannon, 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 Duncannon, PA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 15median — 50% chance of a later frost

Safe for tender plantsMay 2only 10% chance of frost after

First fall frostOctober 23median — 10% chance by Oct 7

Growing season189 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 3 and returns around November 5.

From the NOAA station Harrisburg 1 Ne, PA — 13 miles away, elevation 420 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 17020

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 4 – Mar 18

SpinachSow outdoors · Mar 4 – Mar 25

Broccoli, cabbageStart indoors · Feb 4 – Feb 18

Broccoli, cabbageTransplant · Mar 25 – Apr 8

Onion setsPlant outdoors · Mar 18 – Apr 1

PotatoesPlant outdoors · Mar 25 – Apr 8

LettuceSow outdoors · Mar 18 – Apr 1

Carrots, beetsSow outdoors · Mar 25 – Apr 8

TomatoesStart indoors · Feb 18 – Mar 4

TomatoesTransplant · Apr 22 – May 6

Peppers, eggplantStart indoors · Feb 4 – Feb 18

Peppers, eggplantTransplant · Apr 29 – May 13

BeansSow outdoors · Apr 22 – May 6

Sweet cornSow outdoors · Apr 22 – May 6

Cucumbers, squashSow outdoors · Apr 22 – May 6

Fall lettuce, spinachSow outdoors · Aug 28 – Sep 11

GarlicPlant cloves · Oct 9 – Nov 13

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 15) and first fall frost (Oct 23) 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 17020 came on Mar 22 — 10 days earlier than the 1991–2020 average (Apr 1).

average
Apr 12026
Mar 22

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 Duncannon, PA.

Soil in Duncannon, PA

The soil mapped at the center of ZIP 17020 is Klinesville — channery silt loam, somewhat excessively drained.

TextureChannery silt loama good balance for most vegetables

pH5.3strongly acidic; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Klinesville very shaly silt loam, 15 to 25 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 17020; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Duncannon, PA

Summer high85 °Faverage high, July

Winter low22 °Faverage low, January

Hot days18days a year at 90 °F or more

Freezing nights111nights a year at 32 °F or less

Growing degree days3,209base 50 °F — the season’s usable heat

Longest day15 h 04 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)

Precipitation47.5 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: Harrisburg 1 Ne, PA (13 mi away); precipitation: Enola 1.7 N, PA (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

170697a

New Buffalo, PA · 4 mi

170537a

Marysville, PA · 6 mi

170747a

Newport, PA · 7 mi

170687a

New Bloomfield, PA · 7 mi

170257a

Enola, PA · 9 mi

170937a

Summerdale, PA · 9 mi

170907a

Shermans Dale, PA · 10 mi

171107a

Harrisburg, PA · 10 mi

Pennsylvania planting zones →

Questions about 17020

What planting zone is ZIP code 17020?

ZIP code 17020 (Duncannon, 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 Duncannon, PA?

The median last spring frost (32 °F) near 17020 is April 15; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Harrisburg 1 Ne station.

When is the first frost in Duncannon, PA?

The median first fall frost near 17020 is October 23, giving a median frost-free growing season of 189 days.

When should I plant tomatoes in 17020?

Start tomato seeds indoors around Feb 18 – Mar 4 and set transplants outside around Apr 22 – May 6, one to three weeks after the median last frost.

How much rain and snow does 17020 get?

About 47.5 inches of precipitation a year (NOAA 1991–2020 normals, Enola 1.7 N station).

How hot do summers get in Duncannon, PA?

The average high peaks at 85 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 17020 have?

The USDA soil survey maps Klinesville at the center of ZIP 17020: channery silt loam, somewhat excessively drained, pH about 5.3 (strongly acidic).

Did spring come early in Duncannon, PA in 2026?

Spring leaf-out near 17020 came on Mar 22 in 2026, 10 days earlier than the 1991–2020 average (Apr 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Duncannon, PA?

Long-day onions: the longest day near 17020 is 15 h 04 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 17020 change?

Yes. The 2012 USDA map put 17020 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.