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

Planting zone for 21090 — Linthicum Heights, MD

ZIP code 21090 (Linthicum Heights, Anne Arundel County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 10 and the first fall frost October 31.

Where ZIP 21090 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 frostApr 10

First frostOct 31

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 Linthicum Heights, 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 Linthicum Heights, 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 25only 10% chance of frost after

First fall frostOctober 31median — 10% chance by Oct 17

Growing season204 daysfrost-free, median

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

From the NOAA station Baltimore Wash Intl Airport, MD — 3 miles away, elevation 157 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 21090

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 5 – Sep 19

GarlicPlant cloves · Oct 17 – Nov 21

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Oct 31) 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 21090 came on Mar 12 — about the same time as the 1991–2020 average (Mar 12).

average
Mar 122026
Mar 12

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 Linthicum Heights, MD

The soil mapped at the center of ZIP 21090 is Sassafras — fine sandy loam, well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter4.4%moderate

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Sassafras-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 21090; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Linthicum Heights, MD

Summer high89 °Faverage high, July

Winter low25 °Faverage low, January

Hot days34days a year at 90 °F or more

Freezing nights93nights a year at 32 °F or less

Growing degree days4,007base 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

Precipitation45 inper year, rain and melted snow

Snowfall19 inper year; 13 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Baltimore Wash Intl Airport, MD (3 mi away); precipitation: Baltimore Wash Intl Airport, MD (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

212277b

Halethorpe, MD · 2 mi

Glen Burnie, MD · 4 mi

Maryland planting zones →

Questions about 21090

What planting zone is ZIP code 21090?

ZIP code 21090 (Linthicum Heights, 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 Linthicum Heights, MD?

The median last spring frost (32 °F) near 21090 is April 10; after April 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Baltimore Wash Intl Airport station.

When is the first frost in Linthicum Heights, MD?

The median first fall frost near 21090 is October 31, giving a median frost-free growing season of 204 days.

When should I plant tomatoes in 21090?

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 21090 get?

About 45 inches of precipitation a year and 19 inches of snowfall (NOAA 1991–2020 normals, Baltimore Wash Intl Airport station).

How hot do summers get in Linthicum Heights, MD?

The average high peaks at 89 °F in July, with about 34 days a year at 90 °F or more.

What kind of soil does 21090 have?

The USDA soil survey maps Sassafras at the center of ZIP 21090: fine sandy loam, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Linthicum Heights, MD in 2026?

Spring leaf-out near 21090 came on Mar 12 in 2026, about the same as the 1991–2020 average (Mar 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Linthicum Heights, MD?

Intermediate onions: the longest day near 21090 is 14 h 56 min, so day-neutral types bulb best; long-day varieties may not bulb fully.