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

Planting zone for 21140 — Riva, MD

ZIP code 21140 (Riva, Anne Arundel County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is March 27 and the first fall frost November 13.

Where ZIP 21140 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.

Zone7b5 to 10 °F
Coldest night−15 to −12.2 °C
Last frostMar 27
First frostNov 13
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 Riva, 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 Riva, MD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 27median — 50% chance of a later frost
Safe for tender plantsApril 9only 10% chance of frost after
First fall frostNovember 13median — 10% chance by Nov 1
Growing season234 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 14 and returns around November 28.

From the NOAA station Annapolis Police Brks, MD — 5 miles away, elevation 26 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 21140

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 13 – Feb 27
SpinachSow outdoors · Feb 13 – Mar 6
Broccoli, cabbageStart indoors · Jan 16 – Jan 30
Broccoli, cabbageTransplant · Mar 6 – Mar 20
Onion setsPlant outdoors · Feb 27 – Mar 13
PotatoesPlant outdoors · Mar 6 – Mar 20
LettuceSow outdoors · Feb 27 – Mar 13
Carrots, beetsSow outdoors · Mar 6 – Mar 20
TomatoesStart indoors · Jan 30 – Feb 13
TomatoesTransplant · Apr 3 – Apr 17
Peppers, eggplantStart indoors · Jan 16 – Jan 30
Peppers, eggplantTransplant · Apr 10 – Apr 24
BeansSow outdoors · Apr 3 – Apr 17
Sweet cornSow outdoors · Apr 3 – Apr 17
Cucumbers, squashSow outdoors · Apr 3 – Apr 17
Fall lettuce, spinachSow outdoors · Sep 18 – Oct 2
GarlicPlant cloves · Oct 30 – Dec 4
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 27) and first fall frost (Nov 13) 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 21140 came on Mar 12 — about the same time as the 1991–2020 average (Mar 14).

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 Riva, MD

The soil mapped at the center of ZIP 21140 is Annapolis — fine sandy loam, well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH5.4strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.93%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Annapolis-Urban land complex, 0 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 21140; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Riva, MD

Summer high89 °Faverage high, July
Winter low29 °Faverage low, January
Hot days40days a year at 90 °F or more
Freezing nights81nights a year at 32 °F or less
Growing degree days4,561base 50 °F — the season’s usable heat
Longest day14 h 54 mindaylight on June 21
Shortest day9 h 26 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation45.7 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 29 °F 44°29° JanFebruary: average high 48 °F, low 31 °F 48°31° FebMarch: average high 55 °F, low 38 °F 55°38° MarApril: average high 68 °F, low 48 °F 68°48° AprMay: average high 77 °F, low 57 °F 77°57° MayJune: average high 85 °F, low 67 °F 85°67° JunJuly: average high 89 °F, low 71 °F 89°71° JulAugust: average high 86 °F, low 70 °F 86°70° AugSeptember: average high 80 °F, low 65 °F 80°65° SepOctober: average high 69 °F, low 52 °F 69°52° OctNovember: average high 58 °F, low 41 °F 58°41° NovDecember: average high 48 °F, low 34 °F 48°34° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.17 in precipitation 3.2 JanFebruary: 2.78 in precipitation 2.8 FebMarch: 3.98 in precipitation 4.0 MarApril: 3.14 in precipitation 3.1 AprMay: 4.56 in precipitation 4.6 MayJune: 4.11 in precipitation 4.1 JunJuly: 4.65 in precipitation 4.7 JulAugust: 3.88 in precipitation 3.9 AugSeptember: 4.07 in precipitation 4.1 SepOctober: 4.26 in precipitation 4.3 OctNovember: 3.27 in precipitation 3.3 NovDecember: 3.80 in precipitation 3.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Annapolis Police Brks, MD (5 mi away); precipitation: Birdsville 0.2 Wsw, MD (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

210628a
Glen Burnie, MD · 2 mi
211238a
Pasadena, MD · 2 mi
214118a
Annapolis, MD · 2 mi
214128a
Annapolis, MD · 2 mi
210357b
Davidsonville, MD · 2 mi
214017b
Annapolis, MD · 3 mi
210378a
Edgewater, MD · 3 mi
207767b
Harwood, MD · 5 mi

Maryland planting zones →

Questions about 21140

What planting zone is ZIP code 21140?

ZIP code 21140 (Riva, MD) 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 Riva, MD?

The median last spring frost (32 °F) near 21140 is March 27; after April 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Annapolis Police Brks station.

When is the first frost in Riva, MD?

The median first fall frost near 21140 is November 13, giving a median frost-free growing season of 234 days.

When should I plant tomatoes in 21140?

Start tomato seeds indoors around Jan 30 – Feb 13 and set transplants outside around Apr 3 – Apr 17, one to three weeks after the median last frost.

How much rain and snow does 21140 get?

About 45.7 inches of precipitation a year (NOAA 1991–2020 normals, Birdsville 0.2 Wsw station).

How hot do summers get in Riva, MD?

The average high peaks at 89 °F in July, with about 40 days a year at 90 °F or more.

What kind of soil does 21140 have?

The USDA soil survey maps Annapolis at the center of ZIP 21140: fine sandy loam, well drained, pH about 5.4 (strongly acidic).

Did spring come early in Riva, MD in 2026?

Spring leaf-out near 21140 came on Mar 12 in 2026, about the same as the 1991–2020 average (Mar 14), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Riva, MD?

Intermediate onions: the longest day near 21140 is 14 h 54 min, so day-neutral types bulb best; long-day varieties may not bulb fully.