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

Planting zone for 21220 — Middle River, MD

ZIP code 21220 (Middle River, 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 21220 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 Middle River, 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 Middle River, 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 — 12 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 21220

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 21220 came on Mar 13 — about the same time as the 1991–2020 average (Mar 13).

average
Mar 132026
Mar 13

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 Middle River, MD.

Soil in Middle River, MD

The soil mapped at the center of ZIP 21220 is Sassafras — sandy loam, well drained.

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

pH4.9strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Sassafras-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 21220; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Middle River, 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 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: Md Sci Center Baltimore, MD (12 mi away); precipitation: Kingsville 1.2 E, MD (7 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.

210278a

Chase, MD · 2 mi

211628a

White Marsh, MD · 3 mi

212218a

Essex, MD · 4 mi

211287b

Perry Hall, MD · 5 mi

212378a

Rosedale, MD · 6 mi

212367b

Nottingham, MD · 6 mi

211567b

Upper Falls, MD · 6 mi

210108a

Gunpowder, MD · 6 mi

Maryland planting zones →

Questions about 21220

What planting zone is ZIP code 21220?

ZIP code 21220 (Middle River, 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 Middle River, MD?

The median last spring frost (32 °F) near 21220 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 Middle River, MD?

The median first fall frost near 21220 is November 21, giving a median frost-free growing season of 244 days.

When should I plant tomatoes in 21220?

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 21220 get?

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

How hot do summers get in Middle River, 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 21220 have?

The USDA soil survey maps Sassafras at the center of ZIP 21220: sandy loam, well drained, pH about 4.9 (strongly acidic).

Did spring come early in Middle River, MD in 2026?

Spring leaf-out near 21220 came on Mar 13 in 2026, about the same as the 1991–2020 average (Mar 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Middle River, MD?

Intermediate onions: the longest day near 21220 is 14 h 57 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21220 change?

Yes. The 2012 USDA map put 21220 in zone 7b; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.