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

Planting zone for 22121 — Mount Vernon, VA

ZIP code 22121 (Mount Vernon, Fairfax County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 3 and the first fall frost November 8.

Where ZIP 22121 is

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 3
First frostNov 8
2012 zone7b

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 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Vernon, VA…

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 Vernon, VA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 3median — 50% chance of a later frost
Safe for tender plantsApril 15only 10% chance of frost after
First fall frostNovember 8median — 10% chance by Oct 24
Growing season217 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 21 and returns around November 19.

From the NOAA station Oxon Hill, MD — 8 miles away, elevation 190 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 22121

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 20 – Mar 6
SpinachSow outdoors · Feb 20 – Mar 13
Broccoli, cabbageStart indoors · Jan 23 – Feb 6
Broccoli, cabbageTransplant · Mar 13 – Mar 27
Onion setsPlant outdoors · Mar 6 – Mar 20
PotatoesPlant outdoors · Mar 13 – Mar 27
LettuceSow outdoors · Mar 6 – Mar 20
Carrots, beetsSow outdoors · Mar 13 – Mar 27
TomatoesStart indoors · Feb 6 – Feb 20
TomatoesTransplant · Apr 10 – Apr 24
Peppers, eggplantStart indoors · Jan 23 – Feb 6
Peppers, eggplantTransplant · Apr 17 – May 1
BeansSow outdoors · Apr 10 – Apr 24
Sweet cornSow outdoors · Apr 10 – Apr 24
Cucumbers, squashSow outdoors · Apr 10 – Apr 24
Fall lettuce, spinachSow outdoors · Sep 13 – Sep 27
GarlicPlant cloves · Oct 25 – Nov 29
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 3) and first fall frost (Nov 8) 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 22121 came on Mar 9 — about the same time as the 1991–2020 average (Mar 8).

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 Vernon, VA

The soil mapped at the center of ZIP 22121 is Grist Mill — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH4.8strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.5%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Grist Mill-Mattapex complex, 2 to 7 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 22121; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Vernon, VA

Summer high88 °Faverage high, July
Winter low27 °Faverage low, January
Hot days38days a year at 90 °F or more
Freezing nights80nights a year at 32 °F or less
Growing degree days4,190base 50 °F — the season’s usable heat
Longest day14 h 53 mindaylight on June 21
Shortest day9 h 27 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation47.2 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 44 °F, low 27 °F 44°27° JanFebruary: average high 48 °F, low 28 °F 48°28° FebMarch: average high 56 °F, low 35 °F 56°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 64 °F 84°64° JunJuly: average high 88 °F, low 69 °F 88°69° JulAugust: average high 87 °F, low 67 °F 87°67° AugSeptember: average high 80 °F, low 61 °F 80°61° SepOctober: average high 68 °F, low 48 °F 68°48° OctNovember: average high 57 °F, low 39 °F 57°39° NovDecember: average high 48 °F, low 31 °F 48°31° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.06 in precipitation 3.1 JanFebruary: 2.77 in precipitation 2.8 FebMarch: 4.00 in precipitation 4.0 MarApril: 3.41 in precipitation 3.4 AprMay: 4.53 in precipitation 4.5 MayJune: 5.17 in precipitation 5.2 JunJuly: 4.75 in precipitation 4.8 JulAugust: 4.09 in precipitation 4.1 AugSeptember: 4.49 in precipitation 4.5 SepOctober: 3.92 in precipitation 3.9 OctNovember: 3.22 in precipitation 3.2 NovDecember: 3.76 in precipitation 3.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Oxon Hill, MD (8 mi away); precipitation: Alexandria 5.6 Ssw, VA (within 1 mile). 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.

223097b
Alexandria, VA · <1 mi
220367b
Fairfax, VA · 2 mi
223067b
Alexandria, VA · 2 mi
223088a
Alexandria, VA · 3 mi
220607b
Fort Belvoir, VA · 3 mi
223157b
Alexandria, VA · 3 mi
206167b
Bryans Road, MD · 4 mi
223078a
Alexandria, VA · 4 mi

Virginia planting zones →

Questions about 22121

What planting zone is ZIP code 22121?

ZIP code 22121 (Mount Vernon, VA) 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 Mount Vernon, VA?

The median last spring frost (32 °F) near 22121 is April 3; after April 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Oxon Hill station.

When is the first frost in Mount Vernon, VA?

The median first fall frost near 22121 is November 8, giving a median frost-free growing season of 217 days.

When should I plant tomatoes in 22121?

Start tomato seeds indoors around Feb 6 – Feb 20 and set transplants outside around Apr 10 – Apr 24, one to three weeks after the median last frost.

How much rain and snow does 22121 get?

About 47.2 inches of precipitation a year (NOAA 1991–2020 normals, Alexandria 5.6 Ssw station).

How hot do summers get in Mount Vernon, VA?

The average high peaks at 88 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 22121 have?

The USDA soil survey maps Grist Mill at the center of ZIP 22121: sandy loam, well drained, pH about 4.8 (strongly acidic).

Did spring come early in Mount Vernon, VA in 2026?

Spring leaf-out near 22121 came on Mar 9 in 2026, about the same as the 1991–2020 average (Mar 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Vernon, VA?

Intermediate onions: the longest day near 22121 is 14 h 53 min, so day-neutral types bulb best; long-day varieties may not bulb fully.