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

Planting zone for 03446 — Swanzey, NH

ZIP code 03446 (Swanzey, Cheshire County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 14 and the first fall frost October 1.

Where ZIP 03446 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostMay 14
First frostOct 1
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Swanzey, NH…

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 Swanzey, NH

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 14median — 50% chance of a later frost
Safe for tender plantsMay 28only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 18
Growing season138 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 10.

From the NOAA station Keene, NH — 6 miles away, elevation 512 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 03446

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 2 – Apr 16
SpinachSow outdoors · Apr 2 – Apr 23
Broccoli, cabbageStart indoors · Mar 5 – Mar 19
Broccoli, cabbageTransplant · Apr 23 – May 7
Onion setsPlant outdoors · Apr 16 – Apr 30
PotatoesPlant outdoors · Apr 23 – May 7
LettuceSow outdoors · Apr 16 – Apr 30
Carrots, beetsSow outdoors · Apr 23 – May 7
TomatoesStart indoors · Mar 19 – Apr 2
TomatoesTransplant · May 21 – Jun 4
Peppers, eggplantStart indoors · Mar 5 – Mar 19
Peppers, eggplantTransplant · May 28 – Jun 11
BeansSow outdoors · May 21 – Jun 4
Sweet cornSow outdoors · May 21 – Jun 4
Cucumbers, squashSow outdoors · May 21 – Jun 4
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 14) and first fall frost (Oct 1) 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 03446 came on Apr 12 — 5 days earlier than the 1991–2020 average (Apr 17).

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 5b in New Hampshire

475 plants native to the lower 48 states, recorded in New Hampshire, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 53

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 96

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °F

Wildflowers & perennials 167

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °F

Grasses 141

alpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 6

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °FVirginia creeper1 ft · blooms late spring · medium shade tolerance · to −28 °F

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 Swanzey, NH.

Soil in Swanzey, NH

The soil mapped at the center of ZIP 03446 is Lyme — fine sandy loam, poorly drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter6%high
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Lyme and Moosilauke soils, 0 to 5 percent slopes, very stony.

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 03446; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Swanzey, NH

Summer high82 °Faverage high, July
Winter low10 °Faverage low, January
Hot days11days a year at 90 °F or more
Freezing nights174nights a year at 32 °F or less
Growing degree days2,165base 50 °F — the season’s usable heat
Longest day15 h 21 mindaylight on June 21
Shortest day9 h 01 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation46.1 inper year, rain and melted snow
Snowfall60 inper year; 87 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 30 °F, low 10 °F 30°10° JanFebruary: average high 34 °F, low 11 °F 34°11° FebMarch: average high 43 °F, low 20 °F 43°20° MarApril: average high 57 °F, low 30 °F 57°30° AprMay: average high 69 °F, low 41 °F 69°41° MayJune: average high 77 °F, low 51 °F 77°51° JunJuly: average high 82 °F, low 56 °F 82°56° JulAugust: average high 81 °F, low 54 °F 81°54° AugSeptember: average high 73 °F, low 47 °F 73°47° SepOctober: average high 60 °F, low 36 °F 60°36° OctNovember: average high 47 °F, low 27 °F 47°27° NovDecember: average high 36 °F, low 18 °F 36°18° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.12 in precipitation, 15.2 in snowfall 3.1❄15 JanFebruary: 2.77 in precipitation, 14.4 in snowfall 2.8❄14 FebMarch: 3.35 in precipitation, 11 in snowfall 3.4❄11 MarApril: 3.39 in precipitation, 2.2 in snowfall 3.4❄2 AprMay: 3.77 in precipitation 3.8 MayJune: 4.41 in precipitation 4.4 JunJuly: 4.49 in precipitation 4.5 JulAugust: 4.28 in precipitation 4.3 AugSeptember: 4.26 in precipitation 4.3 SepOctober: 4.86 in precipitation, 0.2 in snowfall 4.9 OctNovember: 3.49 in precipitation, 2.4 in snowfall 3.5❄2 NovDecember: 3.92 in precipitation, 14.4 in snowfall 3.9❄14 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Keene, NH (6 mi away); precipitation: Keene, NH (6 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.

034695b
West Swanzey, NH · 1 mi
034355b
Keene, NH · 5 mi
034626a
Spofford, NH · 5 mi
034656a
Troy, NH · 6 mi
034706a
Winchester, NH · 7 mi
034556a
Marlborough, NH · 7 mi
034315b
Keene, NH · 8 mi
034436a
Chesterfield, NH · 9 mi

New Hampshire planting zones →

Questions about 03446

What planting zone is ZIP code 03446?

ZIP code 03446 (Swanzey, NH) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Swanzey, NH?

The median last spring frost (32 °F) near 03446 is May 14; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Keene station.

When is the first frost in Swanzey, NH?

The median first fall frost near 03446 is October 1, giving a median frost-free growing season of 138 days.

When should I plant tomatoes in 03446?

Start tomato seeds indoors around Mar 19 – Apr 2 and set transplants outside around May 21 – Jun 4, one to three weeks after the median last frost.

How much rain and snow does 03446 get?

About 46.1 inches of precipitation a year and 60 inches of snowfall (NOAA 1991–2020 normals, Keene station).

How hot do summers get in Swanzey, NH?

The average high peaks at 82 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 03446 have?

The USDA soil survey maps Lyme at the center of ZIP 03446: fine sandy loam, poorly drained, pH about 5.0 (strongly acidic).

Did spring come early in Swanzey, NH in 2026?

Spring leaf-out near 03446 came on Apr 12 in 2026, 5 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Swanzey, NH?

Long-day onions: the longest day near 03446 is 15 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).