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

Planting zone for 03240 — Grafton, NH

ZIP code 03240 (Grafton, Grafton County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 21 and the first fall frost September 26.

Where ZIP 03240 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 21
First frostSep 26
2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Grafton, 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 Grafton, NH

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 21median — 50% chance of a later frost
Safe for tender plantsJune 5only 10% chance of frost after
First fall frostSeptember 26median — 10% chance by Sep 12
Growing season127 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 8 and returns around October 5.

From the NOAA station Grafton, NH — within 1 mile, elevation 830 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 03240

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 9 – Apr 23
SpinachSow outdoors · Apr 9 – Apr 30
Broccoli, cabbageStart indoors · Mar 12 – Mar 26
Broccoli, cabbageTransplant · Apr 30 – May 14
Onion setsPlant outdoors · Apr 23 – May 7
PotatoesPlant outdoors · Apr 30 – May 14
LettuceSow outdoors · Apr 23 – May 7
Carrots, beetsSow outdoors · Apr 30 – May 14
TomatoesStart indoors · Mar 26 – Apr 9
TomatoesTransplant · May 28 – Jun 11
Peppers, eggplantStart indoors · Mar 12 – Mar 26
Peppers, eggplantTransplant · Jun 4 – Jun 18
BeansSow outdoors · May 28 – Jun 11
Sweet cornSow outdoors · May 28 – Jun 11
Cucumbers, squashSow outdoors · May 28 – Jun 11
Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15
GarlicPlant cloves · Sep 12 – Oct 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 21) and first fall frost (Sep 26) 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 03240 came on Apr 16 — 7 days earlier than the 1991–2020 average (Apr 23).

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 5a in New Hampshire

467 plants native to the lower 48 states, recorded in New Hampshire, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. Each links to its USDA PLANTS profile.

Trees 52

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 93

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 165

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 140

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 Grafton, NH.

Soil in Grafton, NH

The soil mapped at the center of ZIP 03240 is Skerry — fine sandy loam, moderately well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter7%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Skerry fine sandy loam, 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 03240; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Grafton, NH

Summer high80 °Faverage high, July
Winter low7 °Faverage low, January
Hot days5days a year at 90 °F or more
Freezing nights199nights a year at 32 °F or less
Growing degree days1,846base 50 °F — the season’s usable heat
Longest day15 h 26 mindaylight on June 21
Shortest day8 h 56 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.2 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 29 °F, low 7 °F 29°7° JanFebruary: average high 32 °F, low 7 °F 32°7° FebMarch: average high 40 °F, low 17 °F 40°17° MarApril: average high 54 °F, low 28 °F 54°28° AprMay: average high 66 °F, low 40 °F 66°40° MayJune: average high 75 °F, low 50 °F 75°50° JunJuly: average high 80 °F, low 54 °F 80°54° JulAugust: average high 78 °F, low 53 °F 78°53° AugSeptember: average high 71 °F, low 45 °F 71°45° SepOctober: average high 58 °F, low 33 °F 58°33° OctNovember: average high 45 °F, low 25 °F 45°25° NovDecember: average high 34 °F, low 15 °F 34°15° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.93 in precipitation 2.9 JanFebruary: 2.55 in precipitation 2.5 FebMarch: 3.05 in precipitation 3.0 MarApril: 3.20 in precipitation 3.2 AprMay: 3.18 in precipitation 3.2 MayJune: 4.21 in precipitation 4.2 JunJuly: 3.89 in precipitation 3.9 JulAugust: 3.32 in precipitation 3.3 AugSeptember: 3.23 in precipitation 3.2 SepOctober: 4.51 in precipitation 4.5 OctNovember: 3.11 in precipitation 3.1 NovDecember: 2.98 in precipitation 3.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Grafton, NH (within 1 mile); precipitation: Grafton, NH (within 1 mile). 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.

032305a
Danbury, NH · 5 mi
037495a
Enfield Center, NH · 7 mi
037415a
Canaan, NH · 8 mi
032845b
Springfield, NH · 8 mi
037485a
Enfield, NH · 9 mi
032225b
Bristol, NH · 9 mi
032875b
Wilmot, NH · 9 mi
032435b
Hill, NH · 10 mi

New Hampshire planting zones →

Questions about 03240

What planting zone is ZIP code 03240?

ZIP code 03240 (Grafton, NH) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Grafton, NH?

The median last spring frost (32 °F) near 03240 is May 21; after June 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Grafton station.

When is the first frost in Grafton, NH?

The median first fall frost near 03240 is September 26, giving a median frost-free growing season of 127 days.

When should I plant tomatoes in 03240?

Start tomato seeds indoors around Mar 26 – Apr 9 and set transplants outside around May 28 – Jun 11, one to three weeks after the median last frost.

How much rain and snow does 03240 get?

About 40.2 inches of precipitation a year (NOAA 1991–2020 normals, Grafton station).

How hot do summers get in Grafton, NH?

The average high peaks at 80 °F in July, with about 5 days a year at 90 °F or more.

What kind of soil does 03240 have?

The USDA soil survey maps Skerry at the center of ZIP 03240: fine sandy loam, moderately well drained, pH about 6.0 (slightly acidic).

Did spring come early in Grafton, NH in 2026?

Spring leaf-out near 03240 came on Apr 16 in 2026, 7 days earlier than the 1991–2020 average (Apr 23), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Grafton, NH?

Long-day onions: the longest day near 03240 is 15 h 26 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 03240 change?

Yes. The 2012 USDA map put 03240 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.