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

Planting zone for 21783 — Smithsburg, MD

ZIP code 21783 (Smithsburg, Washington County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 25 and the first fall frost October 19.

Where ZIP 21783 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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 25
First frostOct 19
2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Smithsburg, 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 Smithsburg, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 25median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 19median — 10% chance by Oct 6
Growing season176 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 11 and returns around October 30.

From the NOAA station Smithsburg 2nw, MD — 2 miles away, elevation 669 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 21783

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 14 – Mar 28
SpinachSow outdoors · Mar 14 – Apr 4
Broccoli, cabbageStart indoors · Feb 14 – Feb 28
Broccoli, cabbageTransplant · Apr 4 – Apr 18
Onion setsPlant outdoors · Mar 28 – Apr 11
PotatoesPlant outdoors · Apr 4 – Apr 18
LettuceSow outdoors · Mar 28 – Apr 11
Carrots, beetsSow outdoors · Apr 4 – Apr 18
TomatoesStart indoors · Feb 28 – Mar 14
TomatoesTransplant · May 2 – May 16
Peppers, eggplantStart indoors · Feb 14 – Feb 28
Peppers, eggplantTransplant · May 9 – May 23
BeansSow outdoors · May 2 – May 16
Sweet cornSow outdoors · May 2 – May 16
Cucumbers, squashSow outdoors · May 2 – May 16
Fall lettuce, spinachSow outdoors · Aug 24 – Sep 7
GarlicPlant cloves · Oct 5 – Nov 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 19) 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 21783 came on Mar 22 — 7 days earlier than the 1991–2020 average (Mar 29).

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 Smithsburg, MD

The soil mapped at the center of ZIP 21783 is Bagtown — very stony slightly decomposed plant material, well drained.

TextureVery stony slightly decomposed plant materialtop layer
DrainageWell drainednatural drainage class
Organic matter69%high
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Bagtown cobbly loam, 15 to 25 percent slopes, rubbly.

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 21783; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Smithsburg, MD

Summer high86 °Faverage high, July
Winter low22 °Faverage low, January
Hot days20days a year at 90 °F or more
Freezing nights122nights a year at 32 °F or less
Growing degree days3,218base 50 °F — the season’s usable heat
Longest day14 h 59 mindaylight on June 21
Shortest day9 h 22 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation48.6 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 39 °F, low 22 °F 39°22° JanFebruary: average high 42 °F, low 22 °F 42°22° FebMarch: average high 51 °F, low 29 °F 51°29° MarApril: average high 63 °F, low 39 °F 63°39° AprMay: average high 72 °F, low 49 °F 72°49° MayJune: average high 81 °F, low 59 °F 81°59° JunJuly: average high 86 °F, low 63 °F 86°63° JulAugust: average high 84 °F, low 61 °F 84°61° AugSeptember: average high 77 °F, low 54 °F 77°54° SepOctober: average high 66 °F, low 42 °F 66°42° OctNovember: average high 53 °F, low 32 °F 53°32° NovDecember: average high 43 °F, low 26 °F 43°26° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.77 in precipitation 3.8 JanFebruary: 3.02 in precipitation 3.0 FebMarch: 4.43 in precipitation 4.4 MarApril: 4.02 in precipitation 4.0 AprMay: 4.88 in precipitation 4.9 MayJune: 4.21 in precipitation 4.2 JunJuly: 3.71 in precipitation 3.7 JulAugust: 4.03 in precipitation 4.0 AugSeptember: 5.32 in precipitation 5.3 SepOctober: 4.09 in precipitation 4.1 OctNovember: 3.66 in precipitation 3.7 NovDecember: 3.49 in precipitation 3.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Smithsburg 2nw, MD (2 mi away); precipitation: Catoctin Mtn Park, MD (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

217207a
Cavetown, MD · 2 mi
217807a
Sabillasville, MD · 5 mi
217217a
Chewsville, MD · 5 mi
217197a
Cascade, MD · 5 mi
217427a
Hagerstown, MD · 6 mi
217737a
Myersville, MD · 8 mi
172147a
Blue Ridge Summit, PA · 8 mi
217887a
Thurmont, MD · 9 mi

Maryland planting zones →

Questions about 21783

What planting zone is ZIP code 21783?

ZIP code 21783 (Smithsburg, MD) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Smithsburg, MD?

The median last spring frost (32 °F) near 21783 is April 25; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Smithsburg 2nw station.

When is the first frost in Smithsburg, MD?

The median first fall frost near 21783 is October 19, giving a median frost-free growing season of 176 days.

When should I plant tomatoes in 21783?

Start tomato seeds indoors around Feb 28 – Mar 14 and set transplants outside around May 2 – May 16, one to three weeks after the median last frost.

How much rain and snow does 21783 get?

About 48.6 inches of precipitation a year (NOAA 1991–2020 normals, Catoctin Mtn Park station).

How hot do summers get in Smithsburg, MD?

The average high peaks at 86 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 21783 have?

The USDA soil survey maps Bagtown at the center of ZIP 21783: very stony slightly decomposed plant material, well drained.

Did spring come early in Smithsburg, MD in 2026?

Spring leaf-out near 21783 came on Mar 22 in 2026, 7 days earlier than the 1991–2020 average (Mar 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Smithsburg, MD?

Intermediate onions: the longest day near 21783 is 14 h 59 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 21783 change?

Yes. The 2012 USDA map put 21783 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.