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

Planting zone for New Castle, DE

New Castle, DE is in USDA zone 7b across its 3 ZIP codes. The median last spring frost is April 7 and the first fall frost November 1.

New Castle on the zone map

Outlined: its 1 ZIP code areas · 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.

Zone7b5 to 10 °F
ZIP codes3
Last frostApr 7
First frostNov 1
Growing season209 days

7b 3 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for New Castle, DE…

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 New Castle, DE

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 7median — 50% chance of a later frost
Safe for tender plantsApril 21only 10% chance of frost after
First fall frostNovember 1median — 10% chance by Oct 19
Growing season209 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 27 and returns around November 14.

From the NOAA station Wilmington New Castle Co. Airport, DE, elevation 79 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 New Castle

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 24 – Mar 10
SpinachSow outdoors · Feb 24 – Mar 17
Broccoli, cabbageStart indoors · Jan 27 – Feb 10
Broccoli, cabbageTransplant · Mar 17 – Mar 31
Onion setsPlant outdoors · Mar 10 – Mar 24
PotatoesPlant outdoors · Mar 17 – Mar 31
LettuceSow outdoors · Mar 10 – Mar 24
Carrots, beetsSow outdoors · Mar 17 – Mar 31
TomatoesStart indoors · Feb 10 – Feb 24
TomatoesTransplant · Apr 14 – Apr 28
Peppers, eggplantStart indoors · Jan 27 – Feb 10
Peppers, eggplantTransplant · Apr 21 – May 5
BeansSow outdoors · Apr 14 – Apr 28
Sweet cornSow outdoors · Apr 14 – Apr 28
Cucumbers, squashSow outdoors · Apr 14 – Apr 28
Fall lettuce, spinachSow outdoors · Sep 6 – Sep 20
GarlicPlant cloves · Oct 18 – Nov 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 7) and first fall frost (Nov 1) 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 19720 came on Mar 15 — 3 days earlier than the 1991–2020 average (Mar 18).

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 7b in Delaware

503 plants native to the lower 48 states, recorded in Delaware, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

Trees 65

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 °FAtlantic white cedar50 ft · blooms spring · medium shade tolerance · to −36 °F

Shrubs 103

Allegheny 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 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 170

American 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 °FAmerican spongeplant0.5 ft · blooms mid spring · high shade tolerance · to −24 °F

Grasses 143

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °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 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °F

Vines 10

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °Fmuscadine30 ft · blooms late spring · medium shade tolerance · to −18 °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 New Castle, DE.

Soil in New Castle, DE

The soil mapped at the center of ZIP 19720 is Mattapex — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter1.75%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Mattapex-Urban land complex, 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 19720; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in New Castle, DE

Summer high87 °Faverage high, July
Winter low26 °Faverage low, January
Hot days22days a year at 90 °F or more
Freezing nights92nights a year at 32 °F or less
Growing degree days3,841base 50 °F — the season’s usable heat
Longest day14 h 58 mindaylight on June 21
Shortest day9 h 22 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation45.3 inper year, rain and melted snow
Snowfall20 inper year; 17 days with snow on the ground

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 41 °F, low 26 °F 41°26° JanFebruary: average high 44 °F, low 27 °F 44°27° FebMarch: average high 53 °F, low 34 °F 53°34° MarApril: average high 64 °F, low 44 °F 64°44° AprMay: average high 74 °F, low 53 °F 74°53° MayJune: average high 82 °F, low 63 °F 82°63° JunJuly: average high 87 °F, low 68 °F 87°68° JulAugust: average high 85 °F, low 67 °F 85°67° AugSeptember: average high 79 °F, low 59 °F 79°59° SepOctober: average high 67 °F, low 47 °F 67°47° OctNovember: average high 56 °F, low 37 °F 56°37° NovDecember: average high 46 °F, low 30 °F 46°30° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.23 in precipitation, 6.1 in snowfall 3.2❄6 JanFebruary: 2.83 in precipitation, 7.8 in snowfall 2.8❄8 FebMarch: 4.16 in precipitation, 3.1 in snowfall 4.2❄3 MarApril: 3.51 in precipitation, 0.1 in snowfall 3.5 AprMay: 3.57 in precipitation 3.6 MayJune: 4.67 in precipitation 4.7 JunJuly: 4.41 in precipitation 4.4 JulAugust: 3.98 in precipitation 4.0 AugSeptember: 4.38 in precipitation 4.4 SepOctober: 3.68 in precipitation 3.7 OctNovember: 3.06 in precipitation, 0.2 in snowfall 3.1 NovDecember: 3.85 in precipitation, 2.9 in snowfall 3.9❄3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Wilmington New Castle Co. Airport, DE (2 mi away); precipitation: Wilmington New Castle Co. Airport, DE (2 mi away). Daylight is calculated from latitude.

ZIP codes in New Castle

197207b
5 to 10 °F
197217b
5 to 10 °F
197267b
5 to 10 °F

Delaware planting zones →

Questions about New Castle

What planting zone is New Castle, DE?

New Castle, DE is in USDA hardiness zone 7b on the 2023 map (7b: 5 to 10 °F).

When is the last frost in New Castle, DE?

The median last spring frost is April 7 and the median first fall frost is November 1 (NOAA 1991–2020 normals, Wilmington New Castle Co. Airport station).

When can I plant a garden in New Castle, DE?

Cool-season crops like peas and spinach go in around Feb 24 – Mar 17; tomatoes, peppers, beans and squash after about Apr 14, once frost risk has passed.

What kind of onions grow in New Castle, DE?

Intermediate onions: the longest day is 14 h 58 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

How much rain and snow does New Castle, DE get?

About 45.3 inches of precipitation a year and 20 inches of snowfall (NOAA 1991–2020 normals).