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

Planting zone for 21010 — Gunpowder, MD

ZIP code 21010 (Gunpowder, Harford County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is April 10 and the first fall frost October 30.

Where ZIP 21010 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.

Zone8a10 to 15 °F

Coldest night−12.2 to −9.4 °C

Last frostApr 10

First frostOct 30

2012 zone7b

Was 7b 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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Gunpowder, MD…

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 Gunpowder, MD

JanFebMarAprMayJunJulAugSepOctNovDec

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

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

Safe for tender plantsApril 30only 10% chance of frost after

First fall frostOctober 30median — 10% chance by Oct 14

Growing season201 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 29 and returns around November 10.

From the NOAA station Aberdeen Phillips Field, MD — 9 miles away, elevation 56 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 21010

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 27 – Mar 13

SpinachSow outdoors · Feb 27 – Mar 20

Broccoli, cabbageStart indoors · Jan 30 – Feb 13

Broccoli, cabbageTransplant · Mar 20 – Apr 3

Onion setsPlant outdoors · Mar 13 – Mar 27

PotatoesPlant outdoors · Mar 20 – Apr 3

LettuceSow outdoors · Mar 13 – Mar 27

Carrots, beetsSow outdoors · Mar 20 – Apr 3

TomatoesStart indoors · Feb 13 – Feb 27

TomatoesTransplant · Apr 17 – May 1

Peppers, eggplantStart indoors · Jan 30 – Feb 13

Peppers, eggplantTransplant · Apr 24 – May 8

BeansSow outdoors · Apr 17 – May 1

Sweet cornSow outdoors · Apr 17 – May 1

Cucumbers, squashSow outdoors · Apr 17 – May 1

Fall lettuce, spinachSow outdoors · Sep 4 – Sep 18

GarlicPlant cloves · Oct 16 – Nov 20

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Oct 30) 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 21010 came on Mar 15 — about the same time as the 1991–2020 average (Mar 15).

average
Mar 152026
Mar 15

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 8a in Maryland

629 plants native to the lower 48 states, recorded in Maryland, and rated by the USDA to survive 10 °F or colder — the bottom of zone 8a. 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 Gunpowder, MD.

Soil in Gunpowder, MD

The soil mapped at the center of ZIP 21010 is Udorthents — sandy loam, well drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureSandy loamdrains and warms fast; dries out and needs more feeding

pH4.8strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Urban land-Udorthents complex, 0 to 10 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 21010; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Gunpowder, MD

Summer high86 °Faverage high, July

Winter low25 °Faverage low, January

Hot days26days a year at 90 °F or more

Freezing nights83nights a year at 32 °F or less

Growing degree days3,767base 50 °F — the season’s usable heat

Longest day14 h 57 mindaylight on June 21

Shortest day9 h 23 mindaylight on December 21

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

Precipitation50 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: Aberdeen Phillips Field, MD (9 mi away); precipitation: Kingsville 1.2 E, MD (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

White Marsh, MD · 6 mi

212208a

Middle River, MD · 6 mi

211567b

Upper Falls, MD · 7 mi

210177b

Belcamp, MD · 7 mi

Maryland planting zones →

Questions about 21010

What planting zone is ZIP code 21010?

ZIP code 21010 (Gunpowder, MD) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Gunpowder, MD?

The median last spring frost (32 °F) near 21010 is April 10; after April 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Aberdeen Phillips Field station.

When is the first frost in Gunpowder, MD?

The median first fall frost near 21010 is October 30, giving a median frost-free growing season of 201 days.

When should I plant tomatoes in 21010?

Start tomato seeds indoors around Feb 13 – Feb 27 and set transplants outside around Apr 17 – May 1, one to three weeks after the median last frost.

How much rain and snow does 21010 get?

About 50 inches of precipitation a year (NOAA 1991–2020 normals, Kingsville 1.2 E station).

How hot do summers get in Gunpowder, MD?

The average high peaks at 86 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 21010 have?

The USDA soil survey maps Udorthents at the center of ZIP 21010: sandy loam, well drained, pH about 4.8 (strongly acidic).

Did spring come early in Gunpowder, MD in 2026?

Spring leaf-out near 21010 came on Mar 15 in 2026, about the same as the 1991–2020 average (Mar 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Gunpowder, MD?

Intermediate onions: the longest day near 21010 is 14 h 57 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21010 change?

Yes. The 2012 USDA map put 21010 in zone 7b; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.