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

Planting zone for 28531 — Harkers Island, NC

ZIP code 28531 (Harkers Island, Carteret County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is March 10 and the first fall frost December 1.

Where ZIP 28531 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.

Zone9a20 to 25 °F

Coldest night−6.7 to −3.9 °C

Last frostMar 10

First frostDec 1

2012 zone8a

Was 8a on the 2012 map — a full zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harkers Island, NC…

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 Harkers Island, NC

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMarch 10median — 50% chance of a later frost

Safe for tender plantsMarch 26only 10% chance of frost after

First fall frostDecember 1median — 10% chance by Nov 10

Growing season265 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 23 and returns around December 17.

From the NOAA station Beaufort Michael J Smith Field, NC — 6 miles away, elevation 10 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 28531

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 27 – Feb 10

SpinachSow outdoors · Jan 27 – Feb 17

Broccoli, cabbageStart indoors · Dec 30 – Jan 13

Broccoli, cabbageTransplant · Feb 17 – Mar 3

Onion setsPlant outdoors · Feb 10 – Feb 24

PotatoesPlant outdoors · Feb 17 – Mar 3

LettuceSow outdoors · Feb 10 – Feb 24

Carrots, beetsSow outdoors · Feb 17 – Mar 3

TomatoesStart indoors · Jan 13 – Jan 27

TomatoesTransplant · Mar 17 – Mar 31

Peppers, eggplantStart indoors · Dec 30 – Jan 13

Peppers, eggplantTransplant · Mar 24 – Apr 7

BeansSow outdoors · Mar 17 – Mar 31

Sweet cornSow outdoors · Mar 17 – Mar 31

Cucumbers, squashSow outdoors · Mar 17 – Mar 31

Fall lettuce, spinachSow outdoors · Oct 6 – Oct 20

GarlicPlant cloves · Nov 17 – Dec 22

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 10) and first fall frost (Dec 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 28531 came on Feb 18 — 12 days later than the 1991–2020 average (Feb 6).

average
Feb 62026
Feb 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 9a in North Carolina

643 plants native to the lower 48 states, recorded in North Carolina, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. 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 Harkers Island, NC.

Soil in Harkers Island, NC

The soil mapped at the center of ZIP 28531 is Leon — sand, poorly drained.

TextureSanddrains and warms fast; dries out and needs more feeding

pH5.1strongly acidic; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter2.25%moderate

Hydrologic groupA/Ddrains fast once dried out; wet otherwise

Farmland classFarmland of unique importanceUSDA classification

Map unit: Leon sand.

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 28531; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harkers Island, NC

Summer high87 °Faverage high, July

Winter low38 °Faverage low, January

Hot days7days a year at 90 °F or more

Freezing nights28nights a year at 32 °F or less

Growing degree days5,580base 50 °F — the season’s usable heat

Longest day14 h 29 mindaylight on June 21

Shortest day9 h 49 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation64.1 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: Beaufort Michael J Smith Field, NC (6 mi away); precipitation: Harkers Island 3.2 Ne, NC (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

6 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

285289a

Gloucester, NC · 3 mi

285539a

Marshallberg, NC · 4 mi

Morehead City, NC · 11 mi

North Carolina planting zones →

Questions about 28531

What planting zone is ZIP code 28531?

ZIP code 28531 (Harkers Island, NC) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Harkers Island, NC?

The median last spring frost (32 °F) near 28531 is March 10; after March 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Beaufort Michael J Smith Field station.

When is the first frost in Harkers Island, NC?

The median first fall frost near 28531 is December 1, giving a median frost-free growing season of 265 days.

When should I plant tomatoes in 28531?

Start tomato seeds indoors around Jan 13 – Jan 27 and set transplants outside around Mar 17 – Mar 31, one to three weeks after the median last frost.

How much rain and snow does 28531 get?

About 64.1 inches of precipitation a year (NOAA 1991–2020 normals, Harkers Island 3.2 Ne station).

How hot do summers get in Harkers Island, NC?

The average high peaks at 87 °F in July, with about 7 days a year at 90 °F or more.

What kind of soil does 28531 have?

The USDA soil survey maps Leon at the center of ZIP 28531: sand, poorly drained, pH about 5.1 (strongly acidic).

Did spring come early in Harkers Island, NC in 2026?

Spring leaf-out near 28531 came on Feb 18 in 2026, 12 days later than the 1991–2020 average (Feb 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harkers Island, NC?

Intermediate onions: the longest day near 28531 is 14 h 29 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 28531 change?

Yes. The 2012 USDA map put 28531 in zone 8a; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.