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

Planting zone for 03031 — Amherst, NH

ZIP code 03031 (Amherst, Hillsborough) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 3 and the first fall frost October 5.

Where ZIP 03031 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 3
First frostOct 5
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Amherst, 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 Amherst, NH

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 3median — 50% chance of a later frost
Safe for tender plantsMay 15only 10% chance of frost after
First fall frostOctober 5median — 10% chance by Sep 25
Growing season156 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 20 and returns around October 16.

From the NOAA station Milford, NH — 4 miles away, elevation 322 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 03031

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 22 – Apr 5
SpinachSow outdoors · Mar 22 – Apr 12
Broccoli, cabbageStart indoors · Feb 22 – Mar 8
Broccoli, cabbageTransplant · Apr 12 – Apr 26
Onion setsPlant outdoors · Apr 5 – Apr 19
PotatoesPlant outdoors · Apr 12 – Apr 26
LettuceSow outdoors · Apr 5 – Apr 19
Carrots, beetsSow outdoors · Apr 12 – Apr 26
TomatoesStart indoors · Mar 8 – Mar 22
TomatoesTransplant · May 10 – May 24
Peppers, eggplantStart indoors · Feb 22 – Mar 8
Peppers, eggplantTransplant · May 17 – May 31
BeansSow outdoors · May 10 – May 24
Sweet cornSow outdoors · May 10 – May 24
Cucumbers, squashSow outdoors · May 10 – May 24
Fall lettuce, spinachSow outdoors · Aug 10 – Aug 24
GarlicPlant cloves · Sep 21 – Oct 26
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 3) and first fall frost (Oct 5) 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 03031 came on Apr 9 — 4 days earlier than the 1991–2020 average (Apr 13).

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 Amherst, NH

The soil mapped at the center of ZIP 03031 is Canton — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
DrainageWell drainednatural drainage class
Organic matter95%high
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of local importanceUSDA classification

Map unit: Canton fine sandy loam, 8 to 15 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 03031; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Amherst, NH

Summer high83 °Faverage high, July
Winter low14 °Faverage low, January
Hot days11days a year at 90 °F or more
Freezing nights159nights a year at 32 °F or less
Growing degree days2,495base 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 inper year, rain and melted snow
Snowfall57 inper year; 88 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 33 °F, low 14 °F 33°14° JanFebruary: average high 36 °F, low 15 °F 36°15° FebMarch: average high 45 °F, low 24 °F 45°24° MarApril: average high 58 °F, low 34 °F 58°34° AprMay: average high 69 °F, low 45 °F 69°45° MayJune: average high 78 °F, low 55 °F 78°55° JunJuly: average high 83 °F, low 60 °F 83°60° JulAugust: average high 81 °F, low 58 °F 81°58° AugSeptember: average high 73 °F, low 50 °F 73°50° SepOctober: average high 60 °F, low 38 °F 60°38° OctNovember: average high 49 °F, low 28 °F 49°28° NovDecember: average high 38 °F, low 20 °F 38°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 3.03 in precipitation, 15.4 in snowfall 3.0❄15 JanFebruary: 2.99 in precipitation, 11.5 in snowfall 3.0❄12 FebMarch: 3.79 in precipitation, 14.4 in snowfall 3.8❄14 MarApril: 4.15 in precipitation, 2.3 in snowfall 4.2❄2 AprMay: 3.35 in precipitation 3.4 MayJune: 4.03 in precipitation 4.0 JunJuly: 3.73 in precipitation 3.7 JulAugust: 3.68 in precipitation 3.7 AugSeptember: 4.04 in precipitation 4.0 SepOctober: 4.88 in precipitation, 0.1 in snowfall 4.9 OctNovember: 3.92 in precipitation, 1.1 in snowfall 3.9❄1 NovDecember: 4.45 in precipitation, 12.6 in snowfall 4.5❄13 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Milford, NH (4 mi away); precipitation: Milford, NH (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

030546a
Merrimack, NH · 4 mi
031106a
Bedford, NH · 5 mi
030576a
Mont Vernon, NH · 5 mi
030556a
Milford, NH · 5 mi
030526a
Litchfield, NH · 7 mi
030636a
Nashua, NH · 8 mi
030706a
New Boston, NH · 8 mi
030866a
Wilton, NH · 9 mi

New Hampshire planting zones →

Questions about 03031

What planting zone is ZIP code 03031?

ZIP code 03031 (Amherst, NH) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Amherst, NH?

The median last spring frost (32 °F) near 03031 is May 3; after May 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Milford station.

When is the first frost in Amherst, NH?

The median first fall frost near 03031 is October 5, giving a median frost-free growing season of 156 days.

When should I plant tomatoes in 03031?

Start tomato seeds indoors around Mar 8 – Mar 22 and set transplants outside around May 10 – May 24, one to three weeks after the median last frost.

How much rain and snow does 03031 get?

About 46 inches of precipitation a year and 57 inches of snowfall (NOAA 1991–2020 normals, Milford station).

How hot do summers get in Amherst, NH?

The average high peaks at 83 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 03031 have?

The USDA soil survey maps Canton at the center of ZIP 03031: slightly decomposed plant material, well drained.

Did spring come early in Amherst, NH in 2026?

Spring leaf-out near 03031 came on Apr 9 in 2026, 4 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Amherst, NH?

Long-day onions: the longest day near 03031 is 15 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 03031 change?

Yes. The 2012 USDA map put 03031 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.