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

Planting zone for 21227 — Halethorpe, MD

ZIP code 21227 (Halethorpe, Baltimore County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is March 24 and the first fall frost November 21.

Where ZIP 21227 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.

Zone7b5 to 10 °F
Coldest night−15 to −12.2 °C
Last frostMar 24
First frostNov 21
2012 zone7b

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 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Halethorpe, 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 Halethorpe, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 24median — 50% chance of a later frost
Safe for tender plantsApril 4only 10% chance of frost after
First fall frostNovember 21median — 10% chance by Nov 7
Growing season244 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 11 and returns around December 5.

From the NOAA station Md Sci Center Baltimore, MD — 5 miles away, elevation 20 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 21227

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 10 – Feb 24
SpinachSow outdoors · Feb 10 – Mar 3
Broccoli, cabbageStart indoors · Jan 13 – Jan 27
Broccoli, cabbageTransplant · Mar 3 – Mar 17
Onion setsPlant outdoors · Feb 24 – Mar 10
PotatoesPlant outdoors · Mar 3 – Mar 17
LettuceSow outdoors · Feb 24 – Mar 10
Carrots, beetsSow outdoors · Mar 3 – Mar 17
TomatoesStart indoors · Jan 27 – Feb 10
TomatoesTransplant · Mar 31 – Apr 14
Peppers, eggplantStart indoors · Jan 13 – Jan 27
Peppers, eggplantTransplant · Apr 7 – Apr 21
BeansSow outdoors · Mar 31 – Apr 14
Sweet cornSow outdoors · Mar 31 – Apr 14
Cucumbers, squashSow outdoors · Mar 31 – Apr 14
Fall lettuce, spinachSow outdoors · Sep 26 – Oct 10
GarlicPlant cloves · Nov 7 – Dec 12
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 24) and first fall frost (Nov 21) 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 21227 came on Mar 12 — about the same time as the 1991–2020 average (Mar 11).

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 Maryland

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

Trees 83

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 127

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 beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °F

Wildflowers & perennials 206

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 176

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 12

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 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °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 Halethorpe, MD.

Soil in Halethorpe, MD

The soil mapped at the center of ZIP 21227 is Russett — fine sandy loam, moderately well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH3.9strongly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter5%high
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Russett-Urban land complex, 5 to 15 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 21227; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Halethorpe, MD

Summer high90 °Faverage high, July
Winter low30 °Faverage low, January
Hot days43days a year at 90 °F or more
Freezing nights52nights a year at 32 °F or less
Growing degree days4,686base 50 °F — the season’s usable heat
Longest day14 h 56 mindaylight on June 21
Shortest day9 h 24 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation43.7 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 44 °F, low 30 °F 44°30° JanFebruary: average high 47 °F, low 32 °F 47°32° FebMarch: average high 55 °F, low 39 °F 55°39° MarApril: average high 67 °F, low 48 °F 67°48° AprMay: average high 76 °F, low 58 °F 76°58° MayJune: average high 85 °F, low 68 °F 85°68° JunJuly: average high 90 °F, low 73 °F 90°73° JulAugust: average high 87 °F, low 71 °F 87°71° AugSeptember: average high 80 °F, low 65 °F 80°65° SepOctober: average high 69 °F, low 53 °F 69°53° OctNovember: average high 58 °F, low 43 °F 58°43° NovDecember: average high 48 °F, low 35 °F 48°35° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.07 in precipitation 3.1 JanFebruary: 2.75 in precipitation 2.8 FebMarch: 3.93 in precipitation 3.9 MarApril: 3.55 in precipitation 3.5 AprMay: 3.39 in precipitation 3.4 MayJune: 3.36 in precipitation 3.4 JunJuly: 4.71 in precipitation 4.7 JulAugust: 4.35 in precipitation 4.3 AugSeptember: 4.49 in precipitation 4.5 SepOctober: 3.49 in precipitation 3.5 OctNovember: 2.98 in precipitation 3.0 NovDecember: 3.66 in precipitation 3.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Md Sci Center Baltimore, MD (5 mi away); precipitation: Md Sci Center Baltimore, MD (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

212507b
Baltimore, MD · 2 mi
210907b
Linthicum Heights, MD · 2 mi
212297b
Baltimore, MD · 3 mi
212237b
Baltimore, MD · 3 mi
212308a
Baltimore, MD · 3 mi
212258a
Brooklyn, MD · 4 mi
212287b
Catonsville, MD · 4 mi
212038a
Baltimore, MD · 4 mi

Maryland planting zones →

Questions about 21227

What planting zone is ZIP code 21227?

ZIP code 21227 (Halethorpe, MD) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Halethorpe, MD?

The median last spring frost (32 °F) near 21227 is March 24; after April 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Md Sci Center Baltimore station.

When is the first frost in Halethorpe, MD?

The median first fall frost near 21227 is November 21, giving a median frost-free growing season of 244 days.

When should I plant tomatoes in 21227?

Start tomato seeds indoors around Jan 27 – Feb 10 and set transplants outside around Mar 31 – Apr 14, one to three weeks after the median last frost.

How much rain and snow does 21227 get?

About 43.7 inches of precipitation a year (NOAA 1991–2020 normals, Md Sci Center Baltimore station).

How hot do summers get in Halethorpe, MD?

The average high peaks at 90 °F in July, with about 43 days a year at 90 °F or more.

What kind of soil does 21227 have?

The USDA soil survey maps Russett at the center of ZIP 21227: fine sandy loam, moderately well drained, pH about 3.9 (strongly acidic).

Did spring come early in Halethorpe, MD in 2026?

Spring leaf-out near 21227 came on Mar 12 in 2026, about the same as the 1991–2020 average (Mar 11), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Halethorpe, MD?

Intermediate onions: the longest day near 21227 is 14 h 56 min, so day-neutral types bulb best; long-day varieties may not bulb fully.