Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 30, 2026

Planting zone for 16137 — Mercer, PA

ZIP code 16137 (Mercer, Mercer County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 15 and the first fall frost October 3.

Where ZIP 16137 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 15

First frostOct 3

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 Mercer, 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 Mercer, PA

JanFebMarAprMayJunJulAugSepOctNovDec

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

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

Safe for tender plantsJune 1only 10% chance of frost after

First fall frostOctober 3median — 10% chance by Sep 19

Growing season140 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 3 and returns around October 13.

From the NOAA station Mercer, PA — within 1 mile, elevation 1,221 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 16137

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 3 – Apr 17

SpinachSow outdoors · Apr 3 – Apr 24

Broccoli, cabbageStart indoors · Mar 6 – Mar 20

Broccoli, cabbageTransplant · Apr 24 – May 8

Onion setsPlant outdoors · Apr 17 – May 1

PotatoesPlant outdoors · Apr 24 – May 8

LettuceSow outdoors · Apr 17 – May 1

Carrots, beetsSow outdoors · Apr 24 – May 8

TomatoesStart indoors · Mar 20 – Apr 3

TomatoesTransplant · May 22 – Jun 5

Peppers, eggplantStart indoors · Mar 6 – Mar 20

Peppers, eggplantTransplant · May 29 – Jun 12

BeansSow outdoors · May 22 – Jun 5

Sweet cornSow outdoors · May 22 – Jun 5

Cucumbers, squashSow outdoors · May 22 – Jun 5

Fall lettuce, spinachSow outdoors · Aug 8 – Aug 22

GarlicPlant cloves · Sep 19 – Oct 24

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 15) and first fall frost (Oct 3) 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 16137 came on Mar 21 — 15 days earlier than the 1991–2020 average (Apr 5).

average
Apr 52026
Mar 21

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 Mercer, PA.

Soil in Mercer, PA

The soil mapped at the center of ZIP 16137 is Canfield — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables

pH6.3slightly acidic; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter3.3%moderate

Hydrologic groupC/Dslow when drained; wet otherwise

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Canfield silt loam, 8 to 15 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 16137; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mercer, PA

Summer high82 °Faverage high, July

Winter low16 °Faverage low, January

Hot days6days a year at 90 °F or more

Freezing nights159nights a year at 32 °F or less

Growing degree days2,525base 50 °F — the season’s usable heat

Longest day15 h 09 mindaylight on June 21

Shortest day9 h 12 mindaylight on December 21

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

Precipitation45.2 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: Mercer, PA (within 1 mile); precipitation: Slippery Rock 1 Ssw, PA (16 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

161336a

Jackson Center, PA · 7 mi

161246a

Fredonia, PA · 7 mi

161426a

New Wilmington, PA · 8 mi

Grove City, PA · 10 mi

161536a

Stoneboro, PA · 10 mi

161136a

Clark, PA · 10 mi

Pennsylvania planting zones →

Questions about 16137

What planting zone is ZIP code 16137?

ZIP code 16137 (Mercer, 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 Mercer, PA?

The median last spring frost (32 °F) near 16137 is May 15; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mercer station.

When is the first frost in Mercer, PA?

The median first fall frost near 16137 is October 3, giving a median frost-free growing season of 140 days.

When should I plant tomatoes in 16137?

Start tomato seeds indoors around Mar 20 – Apr 3 and set transplants outside around May 22 – Jun 5, one to three weeks after the median last frost.

How much rain and snow does 16137 get?

About 45.2 inches of precipitation a year (NOAA 1991–2020 normals, Slippery Rock 1 Ssw station).

How hot do summers get in Mercer, PA?

The average high peaks at 82 °F in July, with about 6 days a year at 90 °F or more.

What kind of soil does 16137 have?

The USDA soil survey maps Canfield at the center of ZIP 16137: silt loam, moderately well drained, pH about 6.3 (slightly acidic).

Did spring come early in Mercer, PA in 2026?

Spring leaf-out near 16137 came on Mar 21 in 2026, 15 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mercer, PA?

Long-day onions: the longest day near 16137 is 15 h 09 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 16137 change?

Yes. The 2012 USDA map put 16137 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.