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

Planting zone for 21029 — Clarksville, MD

ZIP code 21029 (Clarksville, Howard County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 5 and the first fall frost November 9.

Where ZIP 21029 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 5
First frostNov 9
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 Clarksville, 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 Clarksville, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 5median — 50% chance of a later frost
Safe for tender plantsApril 19only 10% chance of frost after
First fall frostNovember 9median — 10% chance by Oct 27
Growing season218 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 25 and returns around November 21.

From the NOAA station Laurel 3 W, MD — 9 miles away, elevation 400 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 21029

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 22 – Mar 8
SpinachSow outdoors · Feb 22 – Mar 15
Broccoli, cabbageStart indoors · Jan 25 – Feb 8
Broccoli, cabbageTransplant · Mar 15 – Mar 29
Onion setsPlant outdoors · Mar 8 – Mar 22
PotatoesPlant outdoors · Mar 15 – Mar 29
LettuceSow outdoors · Mar 8 – Mar 22
Carrots, beetsSow outdoors · Mar 15 – Mar 29
TomatoesStart indoors · Feb 8 – Feb 22
TomatoesTransplant · Apr 12 – Apr 26
Peppers, eggplantStart indoors · Jan 25 – Feb 8
Peppers, eggplantTransplant · Apr 19 – May 3
BeansSow outdoors · Apr 12 – Apr 26
Sweet cornSow outdoors · Apr 12 – Apr 26
Cucumbers, squashSow outdoors · Apr 12 – Apr 26
Fall lettuce, spinachSow outdoors · Sep 14 – Sep 28
GarlicPlant cloves · Oct 26 – Nov 30
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 5) and first fall frost (Nov 9) 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 21029 came on Mar 13 — 4 days earlier than the 1991–2020 average (Mar 17).

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 Clarksville, MD

The soil mapped at the center of ZIP 21029 is Glenville — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.8neutral; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter3%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Glenville 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 21029; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Clarksville, MD

Summer high89 °Faverage high, July
Winter low26 °Faverage low, January
Hot days36days a year at 90 °F or more
Freezing nights86nights a year at 32 °F or less
Growing degree days4,262base 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
Precipitation49.7 inper year, rain and melted snow
Snowfall29 inper year

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 43 °F, low 26 °F 43°26° JanFebruary: average high 46 °F, low 28 °F 46°28° FebMarch: average high 55 °F, low 35 °F 55°35° MarApril: average high 67 °F, low 45 °F 67°45° AprMay: average high 76 °F, low 55 °F 76°55° MayJune: average high 84 °F, low 65 °F 84°65° JunJuly: average high 89 °F, low 69 °F 89°69° JulAugust: average high 87 °F, low 68 °F 87°68° AugSeptember: average high 80 °F, low 61 °F 80°61° SepOctober: average high 69 °F, low 50 °F 69°50° OctNovember: average high 57 °F, low 39 °F 57°39° NovDecember: average high 47 °F, low 31 °F 47°31° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.41 in precipitation, 9 in snowfall 3.4❄9 JanFebruary: 2.77 in precipitation, 10 in snowfall 2.8❄10 FebMarch: 4.21 in precipitation, 5.2 in snowfall 4.2❄5 MarApril: 3.70 in precipitation 3.7 AprMay: 5.09 in precipitation 5.1 MayJune: 4.76 in precipitation 4.8 JunJuly: 5.25 in precipitation 5.3 JulAugust: 3.93 in precipitation 3.9 AugSeptember: 4.71 in precipitation 4.7 SepOctober: 4.21 in precipitation 4.2 OctNovember: 3.66 in precipitation, 0.2 in snowfall 3.7 NovDecember: 3.97 in precipitation, 4.1 in snowfall 4.0❄4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Laurel 3 W, MD (9 mi away); precipitation: Columbia 2.3 N, MD (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7b.

210417b
Ellicott City, MD · 2 mi
211507b
Simpsonville, MD · 2 mi
207777b
Highland, MD · 3 mi
210367b
Dayton, MD · 3 mi
208627b
Brinklow, MD · 4 mi
217377b
Glenelg, MD · 4 mi
210447b
Columbia, MD · 4 mi
207597b
Fulton, MD · 4 mi

Maryland planting zones →

Questions about 21029

What planting zone is ZIP code 21029?

ZIP code 21029 (Clarksville, 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 Clarksville, MD?

The median last spring frost (32 °F) near 21029 is April 5; after April 19 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Laurel 3 W station.

When is the first frost in Clarksville, MD?

The median first fall frost near 21029 is November 9, giving a median frost-free growing season of 218 days.

When should I plant tomatoes in 21029?

Start tomato seeds indoors around Feb 8 – Feb 22 and set transplants outside around Apr 12 – Apr 26, one to three weeks after the median last frost.

How much rain and snow does 21029 get?

About 49.7 inches of precipitation a year and 29 inches of snowfall (NOAA 1991–2020 normals, Columbia 2.3 N station).

How hot do summers get in Clarksville, MD?

The average high peaks at 89 °F in July, with about 36 days a year at 90 °F or more.

What kind of soil does 21029 have?

The USDA soil survey maps Glenville at the center of ZIP 21029: silt loam, moderately well drained, pH about 6.8 (neutral).

Did spring come early in Clarksville, MD in 2026?

Spring leaf-out near 21029 came on Mar 13 in 2026, 4 days earlier than the 1991–2020 average (Mar 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Clarksville, MD?

Intermediate onions: the longest day near 21029 is 14 h 56 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21029 change?

Yes. The 2012 USDA map put 21029 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.