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

Planting zone for 21244 — Windsor Mill, MD

ZIP code 21244 (Windsor Mill, Baltimore County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 2 and the first fall frost November 7.

Where ZIP 21244 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 2
First frostNov 7
2012 zone7a

Was 7a 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 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Windsor Mill, 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 Windsor Mill, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 2median — 50% chance of a later frost
Safe for tender plantsApril 13only 10% chance of frost after
First fall frostNovember 7median — 10% chance by Oct 27
Growing season220 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 22 and returns around November 20.

From the NOAA station Cylburn, MD — 7 miles away, elevation 236 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 21244

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 19 – Mar 5
SpinachSow outdoors · Feb 19 – Mar 12
Broccoli, cabbageStart indoors · Jan 22 – Feb 5
Broccoli, cabbageTransplant · Mar 12 – Mar 26
Onion setsPlant outdoors · Mar 5 – Mar 19
PotatoesPlant outdoors · Mar 12 – Mar 26
LettuceSow outdoors · Mar 5 – Mar 19
Carrots, beetsSow outdoors · Mar 12 – Mar 26
TomatoesStart indoors · Feb 5 – Feb 19
TomatoesTransplant · Apr 9 – Apr 23
Peppers, eggplantStart indoors · Jan 22 – Feb 5
Peppers, eggplantTransplant · Apr 16 – Apr 30
BeansSow outdoors · Apr 9 – Apr 23
Sweet cornSow outdoors · Apr 9 – Apr 23
Cucumbers, squashSow outdoors · Apr 9 – Apr 23
Fall lettuce, spinachSow outdoors · Sep 12 – Sep 26
GarlicPlant cloves · Oct 24 – Nov 28
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 2) and first fall frost (Nov 7) 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 21244 came on Mar 13 — 3 days earlier than the 1991–2020 average (Mar 16).

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 Windsor Mill, MD

The soil mapped at the center of ZIP 21244 is Jackland — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH5.8moderately acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classprime farmlandUSDA classification

Map unit: Jackland silt loam, 3 to 8 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 21244; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Windsor Mill, MD

Summer high87 °Faverage high, July
Winter low27 °Faverage low, January
Hot days18days a year at 90 °F or more
Freezing nights92nights a year at 32 °F or less
Growing degree days3,925base 50 °F — the season’s usable heat
Longest day14 h 57 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
Precipitation47.8 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 42 °F, low 27 °F 42°27° JanFebruary: average high 46 °F, low 28 °F 46°28° FebMarch: average high 54 °F, low 34 °F 54°34° MarApril: average high 66 °F, low 45 °F 66°45° AprMay: average high 73 °F, low 55 °F 73°55° MayJune: average high 82 °F, low 64 °F 82°64° JunJuly: average high 87 °F, low 69 °F 87°69° JulAugust: average high 84 °F, low 67 °F 84°67° AugSeptember: average high 77 °F, low 60 °F 77°60° SepOctober: average high 66 °F, low 49 °F 66°49° OctNovember: average high 56 °F, low 39 °F 56°39° NovDecember: average high 46 °F, low 32 °F 46°32° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.37 in precipitation 3.4 JanFebruary: 2.84 in precipitation 2.8 FebMarch: 4.35 in precipitation 4.3 MarApril: 3.53 in precipitation 3.5 AprMay: 4.44 in precipitation 4.4 MayJune: 4.18 in precipitation 4.2 JunJuly: 4.83 in precipitation 4.8 JulAugust: 4.16 in precipitation 4.2 AugSeptember: 4.59 in precipitation 4.6 SepOctober: 4.21 in precipitation 4.2 OctNovember: 3.38 in precipitation 3.4 NovDecember: 3.95 in precipitation 4.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Cylburn, MD (7 mi away); precipitation: Pikesville 1.8 Sw, MD (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

212077b
Gwynn Oak, MD · 3 mi
211337a
Randallstown, MD · 4 mi
211637b
Woodstock, MD · 4 mi
212827b
Pikesville, MD · 4 mi
212087b
Pikesville, MD · 4 mi
212287b
Catonsville, MD · 5 mi
212157b
Baltimore, MD · 5 mi
210437b
Ellicott City, MD · 6 mi

Maryland planting zones →

Questions about 21244

What planting zone is ZIP code 21244?

ZIP code 21244 (Windsor Mill, 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 Windsor Mill, MD?

The median last spring frost (32 °F) near 21244 is April 2; after April 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cylburn station.

When is the first frost in Windsor Mill, MD?

The median first fall frost near 21244 is November 7, giving a median frost-free growing season of 220 days.

When should I plant tomatoes in 21244?

Start tomato seeds indoors around Feb 5 – Feb 19 and set transplants outside around Apr 9 – Apr 23, one to three weeks after the median last frost.

How much rain and snow does 21244 get?

About 47.8 inches of precipitation a year (NOAA 1991–2020 normals, Pikesville 1.8 Sw station).

How hot do summers get in Windsor Mill, MD?

The average high peaks at 87 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 21244 have?

The USDA soil survey maps Jackland at the center of ZIP 21244: silt loam, somewhat poorly drained, pH about 5.8 (moderately acidic).

Did spring come early in Windsor Mill, MD in 2026?

Spring leaf-out near 21244 came on Mar 13 in 2026, 3 days earlier than the 1991–2020 average (Mar 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Windsor Mill, MD?

Intermediate onions: the longest day near 21244 is 14 h 57 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21244 change?

Yes. The 2012 USDA map put 21244 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.