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

Planting zone for 21771 — Mount Airy, MD

ZIP code 21771 (Mount Airy, Frederick County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 14 and the first fall frost October 29.

Where ZIP 21771 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 14
First frostOct 29
2012 zone7a

Same zone as on the 2012 map. 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 Mount Airy, 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 Mount Airy, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 14median — 50% chance of a later frost
Safe for tender plantsMay 2only 10% chance of frost after
First fall frostOctober 29median — 10% chance by Oct 13
Growing season196 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around November 8.

From the NOAA station Damascus 3 Ssw, MD — 10 miles away, elevation 699 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 21771

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 3 – Mar 17
SpinachSow outdoors · Mar 3 – Mar 24
Broccoli, cabbageStart indoors · Feb 3 – Feb 17
Broccoli, cabbageTransplant · Mar 24 – Apr 7
Onion setsPlant outdoors · Mar 17 – Mar 31
PotatoesPlant outdoors · Mar 24 – Apr 7
LettuceSow outdoors · Mar 17 – Mar 31
Carrots, beetsSow outdoors · Mar 24 – Apr 7
TomatoesStart indoors · Feb 17 – Mar 3
TomatoesTransplant · Apr 21 – May 5
Peppers, eggplantStart indoors · Feb 3 – Feb 17
Peppers, eggplantTransplant · Apr 28 – May 12
BeansSow outdoors · Apr 21 – May 5
Sweet cornSow outdoors · Apr 21 – May 5
Cucumbers, squashSow outdoors · Apr 21 – May 5
Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17
GarlicPlant cloves · Oct 15 – Nov 19
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 14) and first fall frost (Oct 29) 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 21771 came on Mar 12 — 8 days earlier than the 1991–2020 average (Mar 20).

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 Mount Airy, MD

The soil mapped at the center of ZIP 21771 is Glenville — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Glenville-Codorus complex, 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 21771; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Airy, MD

Summer high84 °Faverage high, July
Winter low25 °Faverage low, January
Hot days13days a year at 90 °F or more
Freezing nights98nights a year at 32 °F or less
Growing degree days3,528base 50 °F — the season’s usable heat
Longest day14 h 57 mindaylight on June 21
Shortest day9 h 23 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation47.9 inper year, rain and melted snow
Snowfall31 inper year; 26 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 39 °F, low 25 °F 39°25° JanFebruary: average high 43 °F, low 26 °F 43°26° FebMarch: average high 52 °F, low 33 °F 52°33° MarApril: average high 64 °F, low 43 °F 64°43° AprMay: average high 73 °F, low 53 °F 73°53° MayJune: average high 80 °F, low 62 °F 80°62° JunJuly: average high 84 °F, low 66 °F 84°66° JulAugust: average high 83 °F, low 65 °F 83°65° AugSeptember: average high 76 °F, low 58 °F 76°58° SepOctober: average high 65 °F, low 47 °F 65°47° OctNovember: average high 53 °F, low 36 °F 53°36° NovDecember: average high 44 °F, low 30 °F 44°30° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.41 in precipitation, 9.4 in snowfall 3.4❄9 JanFebruary: 2.98 in precipitation, 11.1 in snowfall 3.0❄11 FebMarch: 4.04 in precipitation, 4.8 in snowfall 4.0❄5 MarApril: 3.62 in precipitation, 0.2 in snowfall 3.6 AprMay: 4.35 in precipitation 4.3 MayJune: 4.67 in precipitation 4.7 JunJuly: 4.49 in precipitation 4.5 JulAugust: 4.18 in precipitation 4.2 AugSeptember: 4.76 in precipitation 4.8 SepOctober: 4.01 in precipitation 4.0 OctNovember: 3.49 in precipitation, 0.8 in snowfall 3.5❄1 NovDecember: 3.89 in precipitation, 5.1 in snowfall 3.9❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Damascus 3 Ssw, MD (10 mi away); precipitation: Damascus 3 Ssw, MD (10 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

217927b
Unionville, MD · 6 mi
217657b
Lisbon, MD · 6 mi
217707a
Monrovia, MD · 6 mi
217747a
New Market, MD · 6 mi
217977b
Woodbine, MD · 7 mi
208727b
Damascus, MD · 7 mi
217627a
Libertytown, MD · 8 mi
217767a
New Windsor, MD · 9 mi

Maryland planting zones →

Questions about 21771

What planting zone is ZIP code 21771?

ZIP code 21771 (Mount Airy, 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 Mount Airy, MD?

The median last spring frost (32 °F) near 21771 is April 14; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Damascus 3 Ssw station.

When is the first frost in Mount Airy, MD?

The median first fall frost near 21771 is October 29, giving a median frost-free growing season of 196 days.

When should I plant tomatoes in 21771?

Start tomato seeds indoors around Feb 17 – Mar 3 and set transplants outside around Apr 21 – May 5, one to three weeks after the median last frost.

How much rain and snow does 21771 get?

About 47.9 inches of precipitation a year and 31 inches of snowfall (NOAA 1991–2020 normals, Damascus 3 Ssw station).

How hot do summers get in Mount Airy, MD?

The average high peaks at 84 °F in July, with about 13 days a year at 90 °F or more.

What kind of soil does 21771 have?

The USDA soil survey maps Glenville at the center of ZIP 21771: silt loam, moderately well drained, pH about 6.0 (slightly acidic).

Did spring come early in Mount Airy, MD in 2026?

Spring leaf-out near 21771 came on Mar 12 in 2026, 8 days earlier than the 1991–2020 average (Mar 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Airy, MD?

Intermediate onions: the longest day near 21771 is 14 h 57 min, so day-neutral types bulb best; long-day varieties may not bulb fully.