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

Planting zone for 20625 — Cobb Island, MD

ZIP code 20625 (Cobb Island, Charles County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is April 17 and the first fall frost October 27.

Where ZIP 20625 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 frostApr 17
First frostOct 27
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 Cobb Island, 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 Cobb Island, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 17median — 50% chance of a later frost
Safe for tender plantsMay 2only 10% chance of frost after
First fall frostOctober 27median — 10% chance by Oct 12
Growing season195 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around November 6.

From the NOAA station Mechanicsville 5 Ne, MD — 17 miles away, elevation 102 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 20625

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 6 – Mar 20
SpinachSow outdoors · Mar 6 – Mar 27
Broccoli, cabbageStart indoors · Feb 6 – Feb 20
Broccoli, cabbageTransplant · Mar 27 – Apr 10
Onion setsPlant outdoors · Mar 20 – Apr 3
PotatoesPlant outdoors · Mar 27 – Apr 10
LettuceSow outdoors · Mar 20 – Apr 3
Carrots, beetsSow outdoors · Mar 27 – Apr 10
TomatoesStart indoors · Feb 20 – Mar 6
TomatoesTransplant · Apr 24 – May 8
Peppers, eggplantStart indoors · Feb 6 – Feb 20
Peppers, eggplantTransplant · May 1 – May 15
BeansSow outdoors · Apr 24 – May 8
Sweet cornSow outdoors · Apr 24 – May 8
Cucumbers, squashSow outdoors · Apr 24 – May 8
Fall lettuce, spinachSow outdoors · Sep 1 – Sep 15
GarlicPlant cloves · Oct 13 – Nov 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 17) and first fall frost (Oct 27) 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 20625 came on Mar 9 — 4 days later than the 1991–2020 average (Mar 5).

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.

Trees 84

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 129

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican beautyberry6 ft · blooms early summer · medium shade tolerance · to −8 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °F

Wildflowers & perennials 209

American bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °FAmerican spongeplant0.5 ft · blooms mid spring · high shade tolerance · to −24 °F

Grasses 181

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

Vines 12

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fgraybark grape50 ft · blooms late spring · medium shade tolerance · to −8 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °F

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 Cobb Island, MD.

Soil in Cobb Island, MD

The soil mapped at the center of ZIP 20625 is Piccowaxen — loam, somewhat poorly drained.

TextureLoama good balance for most vegetables
pH5.1strongly acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter4.1%moderate
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Piccowaxen loam, 0 to 2 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 20625; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cobb Island, MD

Summer high85 °Faverage high, July
Winter low25 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights98nights a year at 32 °F or less
Growing degree days3,649base 50 °F — the season’s usable heat
Longest day14 h 50 mindaylight on June 21
Shortest day9 h 30 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation46.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 44 °F, low 25 °F 44°25° JanFebruary: average high 48 °F, low 26 °F 48°26° FebMarch: average high 56 °F, low 33 °F 56°33° MarApril: average high 67 °F, low 43 °F 67°43° AprMay: average high 74 °F, low 52 °F 74°52° MayJune: average high 82 °F, low 61 °F 82°61° JunJuly: average high 85 °F, low 66 °F 85°66° JulAugust: average high 83 °F, low 64 °F 83°64° AugSeptember: average high 77 °F, low 58 °F 77°58° SepOctober: average high 66 °F, low 46 °F 66°46° OctNovember: average high 57 °F, low 36 °F 57°36° NovDecember: average high 48 °F, low 29 °F 48°29° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.27 in precipitation 3.3 JanFebruary: 2.88 in precipitation 2.9 FebMarch: 3.90 in precipitation 3.9 MarApril: 3.35 in precipitation 3.4 AprMay: 4.30 in precipitation 4.3 MayJune: 4.27 in precipitation 4.3 JunJuly: 3.85 in precipitation 3.9 JulAugust: 4.98 in precipitation 5.0 AugSeptember: 4.47 in precipitation 4.5 SepOctober: 4.68 in precipitation 4.7 OctNovember: 3.22 in precipitation 3.2 NovDecember: 3.40 in precipitation 3.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mechanicsville 5 Ne, MD (17 mi away); precipitation: Montross 5.2 Ese, VA (14 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.

206617b
Mount Victoria, MD · <1 mi
206828a
Rock Point, MD · 2 mi
206188a
Bushwood, MD · 3 mi
206268a
Coltons Point, MD · 5 mi
206457b
Issue, MD · 5 mi
206217b
Chaptico, MD · 5 mi
206098a
Avenue, MD · 5 mi
206068a
Abell, MD · 5 mi

Maryland planting zones →

Questions about 20625

What planting zone is ZIP code 20625?

ZIP code 20625 (Cobb Island, 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 Cobb Island, MD?

The median last spring frost (32 °F) near 20625 is April 17; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mechanicsville 5 Ne station.

When is the first frost in Cobb Island, MD?

The median first fall frost near 20625 is October 27, giving a median frost-free growing season of 195 days.

When should I plant tomatoes in 20625?

Start tomato seeds indoors around Feb 20 – Mar 6 and set transplants outside around Apr 24 – May 8, one to three weeks after the median last frost.

How much rain and snow does 20625 get?

About 46.6 inches of precipitation a year (NOAA 1991–2020 normals, Montross 5.2 Ese station).

How hot do summers get in Cobb Island, MD?

The average high peaks at 85 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 20625 have?

The USDA soil survey maps Piccowaxen at the center of ZIP 20625: loam, somewhat poorly drained, pH about 5.1 (strongly acidic).

Did spring come early in Cobb Island, MD in 2026?

Spring leaf-out near 20625 came on Mar 9 in 2026, 4 days later than the 1991–2020 average (Mar 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cobb Island, MD?

Intermediate onions: the longest day near 20625 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 20625 change?

Yes. The 2012 USDA map put 20625 in zone 7b; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.