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

Planting zone for 16833 — Curwensville, PA

ZIP code 16833 (Curwensville, Clearfield 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 13.

Where ZIP 16833 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 13
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 Curwensville, 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 Curwensville, 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 13median — 10% chance by Sep 30
Growing season160 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 23 and returns around October 27.

From the NOAA station Grampian 1e, PA — 2 miles away, elevation 1,509 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 16833

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 18 – Sep 1
GarlicPlant cloves · Sep 29 – Nov 3
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 4) and first fall frost (Oct 13) 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 16833 came on Mar 27 — 12 days earlier than the 1991–2020 average (Apr 8).

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.

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 121

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 207

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 170

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 9

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 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 Curwensville, PA.

Soil in Curwensville, PA

The soil mapped at the center of ZIP 16833 is Bethesda — channery silt loam, well drained.

TextureChannery silt loama good balance for most vegetables
pH5.2strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.1%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Bethesda-Fairpoint channery silt loams, 25 to 75 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 16833; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Curwensville, PA

Summer high81 °Faverage high, July
Winter low14 °Faverage low, January
Hot days3days a year at 90 °F or more
Freezing nights156nights a year at 32 °F or less
Growing degree days2,345base 50 °F — the season’s usable heat
Longest day15 h 07 mindaylight on June 21
Shortest day9 h 14 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation48.3 inper year, rain and melted snow
Snowfall63 inper year; 76 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 32 °F, low 14 °F 32°14° JanFebruary: average high 36 °F, low 15 °F 36°15° FebMarch: average high 45 °F, low 23 °F 45°23° MarApril: average high 59 °F, low 33 °F 59°33° AprMay: average high 69 °F, low 45 °F 69°45° MayJune: average high 77 °F, low 54 °F 77°54° JunJuly: average high 81 °F, low 58 °F 81°58° JulAugust: average high 79 °F, low 56 °F 79°56° AugSeptember: average high 72 °F, low 49 °F 72°49° SepOctober: average high 61 °F, low 38 °F 61°38° OctNovember: average high 48 °F, low 28 °F 48°28° NovDecember: average high 37 °F, low 21 °F 37°21° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.62 in precipitation, 18.8 in snowfall 3.6❄19 JanFebruary: 3.45 in precipitation, 18 in snowfall 3.5❄18 FebMarch: 3.69 in precipitation, 8.2 in snowfall 3.7❄8 MarApril: 4.22 in precipitation, 2.4 in snowfall 4.2❄2 AprMay: 4.05 in precipitation, 0.1 in snowfall 4.0 MayJune: 5.16 in precipitation 5.2 JunJuly: 4.51 in precipitation 4.5 JulAugust: 4.13 in precipitation 4.1 AugSeptember: 3.94 in precipitation 3.9 SepOctober: 3.87 in precipitation, 0.8 in snowfall 3.9❄1 OctNovember: 3.50 in precipitation, 2.9 in snowfall 3.5❄3 NovDecember: 4.20 in precipitation, 11.8 in snowfall 4.2❄12 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Grampian 1e, PA (2 mi away); precipitation: Grampian 1e, PA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

168376a
Glen Richey, PA · 5 mi
168616a
New Millport, PA · 6 mi
168636a
Olanta, PA · 6 mi
168386a
Grampian, PA · 6 mi
168436a
Hyde, PA · 7 mi
166816a
Smokerun, PA · 8 mi
157576a
Mahaffey, PA · 9 mi
158486a
Luthersburg, PA · 9 mi

Pennsylvania planting zones →

Questions about 16833

What planting zone is ZIP code 16833?

ZIP code 16833 (Curwensville, 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 Curwensville, PA?

The median last spring frost (32 °F) near 16833 is May 4; after May 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Grampian 1e station.

When is the first frost in Curwensville, PA?

The median first fall frost near 16833 is October 13, giving a median frost-free growing season of 160 days.

When should I plant tomatoes in 16833?

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 16833 get?

About 48.3 inches of precipitation a year and 63 inches of snowfall (NOAA 1991–2020 normals, Grampian 1e station).

How hot do summers get in Curwensville, PA?

The average high peaks at 81 °F in July, with about 3 days a year at 90 °F or more.

What kind of soil does 16833 have?

The USDA soil survey maps Bethesda at the center of ZIP 16833: channery silt loam, well drained, pH about 5.2 (strongly acidic).

Did spring come early in Curwensville, PA in 2026?

Spring leaf-out near 16833 came on Mar 27 in 2026, 12 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Curwensville, PA?

Long-day onions: the longest day near 16833 is 15 h 07 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).