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

Planting zone for 08620 — Trenton, NJ

ZIP code 08620 (Trenton, Mercer County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 25 and the first fall frost October 16.

Where ZIP 08620 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 25
First frostOct 16
2012 zone7a

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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Trenton, NJ…

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 Trenton, NJ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 25median — 50% chance of a later frost
Safe for tender plantsMay 12only 10% chance of frost after
First fall frostOctober 16median — 10% chance by Oct 4
Growing season173 daysfrost-free, median

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

From the NOAA station Hightstown 2 W, NJ — 8 miles away, elevation 102 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 08620

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 14 – Mar 28
SpinachSow outdoors · Mar 14 – Apr 4
Broccoli, cabbageStart indoors · Feb 14 – Feb 28
Broccoli, cabbageTransplant · Apr 4 – Apr 18
Onion setsPlant outdoors · Mar 28 – Apr 11
PotatoesPlant outdoors · Apr 4 – Apr 18
LettuceSow outdoors · Mar 28 – Apr 11
Carrots, beetsSow outdoors · Apr 4 – Apr 18
TomatoesStart indoors · Feb 28 – Mar 14
TomatoesTransplant · May 2 – May 16
Peppers, eggplantStart indoors · Feb 14 – Feb 28
Peppers, eggplantTransplant · May 9 – May 23
BeansSow outdoors · May 2 – May 16
Sweet cornSow outdoors · May 2 – May 16
Cucumbers, squashSow outdoors · May 2 – May 16
Fall lettuce, spinachSow outdoors · Aug 21 – Sep 4
GarlicPlant cloves · Oct 2 – Nov 6
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 16) 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 08620 came on Mar 22 — about the same time as the 1991–2020 average (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 New Jersey

600 plants native to the lower 48 states, recorded in New Jersey, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

Trees 80

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 119

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 201

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 lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °F

Grasses 175

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

Vines 10

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °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 °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 Trenton, NJ.

Soil in Trenton, NJ

The soil mapped at the center of ZIP 08620 is Evesboro — loamy sand, excessively drained.

TextureLoamy sanddrains and warms fast; dries out and needs more feeding
pH4.3strongly acidic; most vegetables like 6.0–7.0
DrainageExcessively drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classFarmland of local importanceUSDA classification

Map unit: Evesboro loamy sand, 0 to 5 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 08620; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Trenton, NJ

Summer high87 °Faverage high, July
Winter low21 °Faverage low, January
Hot days26days a year at 90 °F or more
Freezing nights114nights a year at 32 °F or less
Growing degree days3,272base 50 °F — the season’s usable heat
Longest day15 h 02 mindaylight on June 21
Shortest day9 h 18 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation48 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 41 °F, low 21 °F 41°21° JanFebruary: average high 43 °F, low 23 °F 43°23° FebMarch: average high 51 °F, low 30 °F 51°30° MarApril: average high 63 °F, low 39 °F 63°39° AprMay: average high 73 °F, low 48 °F 73°48° MayJune: average high 82 °F, low 58 °F 82°58° JunJuly: average high 87 °F, low 63 °F 87°63° JulAugust: average high 85 °F, low 61 °F 85°61° AugSeptember: average high 78 °F, low 54 °F 78°54° SepOctober: average high 66 °F, low 42 °F 66°42° OctNovember: average high 55 °F, low 33 °F 55°33° NovDecember: average high 46 °F, low 27 °F 46°27° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.58 in precipitation 3.6 JanFebruary: 2.78 in precipitation 2.8 FebMarch: 4.28 in precipitation 4.3 MarApril: 3.59 in precipitation 3.6 AprMay: 4.08 in precipitation 4.1 MayJune: 4.48 in precipitation 4.5 JunJuly: 4.96 in precipitation 5.0 JulAugust: 4.47 in precipitation 4.5 AugSeptember: 4.19 in precipitation 4.2 SepOctober: 3.89 in precipitation 3.9 OctNovember: 3.27 in precipitation 3.3 NovDecember: 4.43 in precipitation 4.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hightstown 2 W, NJ (8 mi away); precipitation: Hamilton Twp 2.3 Ne, NJ (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

085157a
Chesterfield, NJ · 4 mi
086917a
Trenton, NJ · 4 mi
086107a
Trenton, NJ · 4 mi
085057a
Bordentown, NJ · 4 mi
086907a
Trenton, NJ · 4 mi
086117a
Trenton, NJ · 5 mi
085017a
Allentown, NJ · 5 mi
086297a
Trenton, NJ · 5 mi

All 25 ZIP codes in Trenton → · New Jersey planting zones →

Questions about 08620

What planting zone is ZIP code 08620?

ZIP code 08620 (Trenton, NJ) 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 Trenton, NJ?

The median last spring frost (32 °F) near 08620 is April 25; after May 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hightstown 2 W station.

When is the first frost in Trenton, NJ?

The median first fall frost near 08620 is October 16, giving a median frost-free growing season of 173 days.

When should I plant tomatoes in 08620?

Start tomato seeds indoors around Feb 28 – Mar 14 and set transplants outside around May 2 – May 16, one to three weeks after the median last frost.

How much rain and snow does 08620 get?

About 48 inches of precipitation a year (NOAA 1991–2020 normals, Hamilton Twp 2.3 Ne station).

How hot do summers get in Trenton, NJ?

The average high peaks at 87 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 08620 have?

The USDA soil survey maps Evesboro at the center of ZIP 08620: loamy sand, excessively drained, pH about 4.3 (strongly acidic).

Did spring come early in Trenton, NJ in 2026?

Spring leaf-out near 08620 came on Mar 22 in 2026, about the same as the 1991–2020 average (Mar 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Trenton, NJ?

Long-day onions: the longest day near 08620 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).