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

Planting zone for 20629 — Dowell, MD

ZIP code 20629 (Dowell, Calvert County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is March 22 and the first fall frost November 26.

Where ZIP 20629 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 22

First frostNov 26

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 Dowell, 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 Dowell, MD

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMarch 22median — 50% chance of a later frost

Safe for tender plantsApril 5only 10% chance of frost after

First fall frostNovember 26median — 10% chance by Nov 10

Growing season248 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 10 and returns around December 9.

From the NOAA station Solomons, MD — 2 miles away, elevation 13 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 20629

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 8 – Feb 22

SpinachSow outdoors · Feb 8 – Mar 1

Broccoli, cabbageStart indoors · Jan 11 – Jan 25

Broccoli, cabbageTransplant · Mar 1 – Mar 15

Onion setsPlant outdoors · Feb 22 – Mar 8

PotatoesPlant outdoors · Mar 1 – Mar 15

LettuceSow outdoors · Feb 22 – Mar 8

Carrots, beetsSow outdoors · Mar 1 – Mar 15

TomatoesStart indoors · Jan 25 – Feb 8

TomatoesTransplant · Mar 29 – Apr 12

Peppers, eggplantStart indoors · Jan 11 – Jan 25

Peppers, eggplantTransplant · Apr 5 – Apr 19

BeansSow outdoors · Mar 29 – Apr 12

Sweet cornSow outdoors · Mar 29 – Apr 12

Cucumbers, squashSow outdoors · Mar 29 – Apr 12

Fall lettuce, spinachSow outdoors · Oct 1 – Oct 15

GarlicPlant cloves · Nov 12 – Dec 17

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 22) and first fall frost (Nov 26) 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 20629 came on Mar 10 — 4 days later than the 1991–2020 average (Mar 6).

average
Mar 62026
Mar 10

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 Dowell, MD.

Soil in Dowell, MD

The soil mapped at the center of ZIP 20629 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, 2 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 20629; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Dowell, MD

Summer high88 °Faverage high, July

Winter low30 °Faverage low, January

Hot days31days a year at 90 °F or more

Freezing nights59nights a year at 32 °F or less

Growing degree days4,559base 50 °F — the season’s usable heat

Longest day14 h 50 mindaylight on June 21

Shortest day9 h 29 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation45.3 inper year, rain and melted snow

Snowfall13 inper year; 7 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: Solomons, MD (2 mi away); precipitation: Patuxent River NAS, MD (4 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.

Patuxent River, MD · 5 mi

206197b

California, MD · 5 mi

206367b

Hollywood, MD · 6 mi

206158a

Broomes Island, MD · 7 mi

206858a

Saint Leonard, MD · 7 mi

206348a

Great Mills, MD · 7 mi

Maryland planting zones →

Questions about 20629

What planting zone is ZIP code 20629?

ZIP code 20629 (Dowell, 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 Dowell, MD?

The median last spring frost (32 °F) near 20629 is March 22; after April 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Solomons station.

When is the first frost in Dowell, MD?

The median first fall frost near 20629 is November 26, giving a median frost-free growing season of 248 days.

When should I plant tomatoes in 20629?

Start tomato seeds indoors around Jan 25 – Feb 8 and set transplants outside around Mar 29 – Apr 12, one to three weeks after the median last frost.

How much rain and snow does 20629 get?

About 45.3 inches of precipitation a year and 13 inches of snowfall (NOAA 1991–2020 normals, Patuxent River NAS station).

How hot do summers get in Dowell, MD?

The average high peaks at 88 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 20629 have?

The USDA soil survey maps Piccowaxen at the center of ZIP 20629: loam, somewhat poorly drained, pH about 5.1 (strongly acidic).

Did spring come early in Dowell, MD in 2026?

Spring leaf-out near 20629 came on Mar 10 in 2026, 4 days later than the 1991–2020 average (Mar 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Dowell, MD?

Intermediate onions: the longest day near 20629 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 20629 change?

Yes. The 2012 USDA map put 20629 in zone 7b; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.