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

Planting zone for 21222 — Dundalk, MD

ZIP code 21222 (Dundalk, Baltimore County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is March 24 and the first fall frost November 21.

Where ZIP 21222 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 frostMar 24
First frostNov 21
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 Dundalk, 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 Dundalk, 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 — 6 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 21222

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 21222 came on Mar 13 — 3 days later than the 1991–2020 average (Mar 10).

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).

Soil in Dundalk, MD

The soil mapped at the center of ZIP 21222 is Udorthents — silt loam, well drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureSilt loama good balance for most vegetables
pH5.8moderately 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 8 percent.

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 21222; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Dundalk, 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 (6 mi away); precipitation: Md Sci Center Baltimore, MD (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 8a.

212248a
Baltimore, MD · 3 mi
212218a
Essex, MD · 4 mi
212198a
Sparrows Point, MD · 4 mi
212058a
Baltimore, MD · 4 mi
210528a
Fort Howard, MD · 5 mi
212268a
Curtis Bay, MD · 5 mi
212378a
Rosedale, MD · 5 mi
212318a
Baltimore, MD · 5 mi

Maryland planting zones →

Questions about 21222

What planting zone is ZIP code 21222?

ZIP code 21222 (Dundalk, 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 Dundalk, MD?

The median last spring frost (32 °F) near 21222 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 Dundalk, MD?

The median first fall frost near 21222 is November 21, giving a median frost-free growing season of 244 days.

When should I plant tomatoes in 21222?

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 21222 get?

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

How hot do summers get in Dundalk, 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 21222 have?

The USDA soil survey maps Udorthents at the center of ZIP 21222: silt loam, well drained, pH about 5.8 (moderately acidic).

Did spring come early in Dundalk, MD in 2026?

Spring leaf-out near 21222 came on Mar 13 in 2026, 3 days later than the 1991–2020 average (Mar 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Dundalk, MD?

Intermediate onions: the longest day near 21222 is 14 h 56 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21222 change?

Yes. The 2012 USDA map put 21222 in zone 7b; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.