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

Planting zone for 03746 — Cornish Flat, NH

ZIP code 03746 (Cornish Flat, Sullivan County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 8 and the first fall frost October 6.

Where ZIP 03746 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 8
First frostOct 6
2012 zone5a

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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cornish Flat, 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 Cornish Flat, NH

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 8median — 50% chance of a later frost
Safe for tender plantsMay 22only 10% chance of frost after
First fall frostOctober 6median — 10% chance by Sep 25
Growing season150 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 27 and returns around October 17.

From the NOAA station N Hartland Lake, VT — 8 miles away, elevation 571 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 03746

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 27 – Apr 10
SpinachSow outdoors · Mar 27 – Apr 17
Broccoli, cabbageStart indoors · Feb 27 – Mar 13
Broccoli, cabbageTransplant · Apr 17 – May 1
Onion setsPlant outdoors · Apr 10 – Apr 24
PotatoesPlant outdoors · Apr 17 – May 1
LettuceSow outdoors · Apr 10 – Apr 24
Carrots, beetsSow outdoors · Apr 17 – May 1
TomatoesStart indoors · Mar 13 – Mar 27
TomatoesTransplant · May 15 – May 29
Peppers, eggplantStart indoors · Feb 27 – Mar 13
Peppers, eggplantTransplant · May 22 – Jun 5
BeansSow outdoors · May 15 – May 29
Sweet cornSow outdoors · May 15 – May 29
Cucumbers, squashSow outdoors · May 15 – May 29
Fall lettuce, spinachSow outdoors · Aug 11 – Aug 25
GarlicPlant cloves · Sep 22 – Oct 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 8) and first fall frost (Oct 6) 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 03746 came on Apr 16 — 4 days earlier than the 1991–2020 average (Apr 20).

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 Cornish Flat, NH.

Soil in Cornish Flat, NH

The soil mapped at the center of ZIP 03746 is Haven — very fine sandy loam, well drained.

TextureVery fine sandy loamdrains and warms fast; dries out and needs more feeding
pH5.3strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4%moderate
Hydrologic groupBwater soaks in moderately
Farmland classprime farmlandUSDA classification

Map unit: Haven very fine sandy loam, 0 to 3 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 03746; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cornish Flat, NH

Summer high80 °Faverage high, July
Winter low8 °Faverage low, January
Hot days5days a year at 90 °F or more
Freezing nights173nights a year at 32 °F or less
Growing degree days2,083base 50 °F — the season’s usable heat
Longest day15 h 25 mindaylight on June 21
Shortest day8 h 57 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation38.1 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 28 °F, low 8 °F 28°8° JanFebruary: average high 32 °F, low 10 °F 32°10° FebMarch: average high 40 °F, low 18 °F 40°18° MarApril: average high 55 °F, low 30 °F 55°30° AprMay: average high 67 °F, low 42 °F 67°42° MayJune: average high 75 °F, low 52 °F 75°52° JunJuly: average high 80 °F, low 57 °F 80°57° JulAugust: average high 78 °F, low 55 °F 78°55° AugSeptember: average high 71 °F, low 48 °F 71°48° SepOctober: average high 57 °F, low 37 °F 57°37° OctNovember: average high 45 °F, low 27 °F 45°27° NovDecember: average high 34 °F, low 16 °F 34°16° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.29 in precipitation 2.3 JanFebruary: 2.10 in precipitation 2.1 FebMarch: 2.70 in precipitation 2.7 MarApril: 2.99 in precipitation 3.0 AprMay: 3.32 in precipitation 3.3 MayJune: 3.80 in precipitation 3.8 JunJuly: 3.99 in precipitation 4.0 JulAugust: 3.62 in precipitation 3.6 AugSeptember: 3.44 in precipitation 3.4 SepOctober: 4.00 in precipitation 4.0 OctNovember: 2.98 in precipitation 3.0 NovDecember: 2.84 in precipitation 2.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: N Hartland Lake, VT (8 mi away); precipitation: Lebanon Municipal Airport, NH (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

037455b
Cornish, NH · 2 mi
037705a
Meriden, NH · 3 mi
037815a
Plainfield, NH · 4 mi
037535a
Grantham, NH · 7 mi
050525a
North Hartland, VT · 8 mi
050495a
Hartland Four Corners, VT · 8 mi
050895b
Windsor, VT · 8 mi
050305b
Ascutney, VT · 9 mi

New Hampshire planting zones →

Questions about 03746

What planting zone is ZIP code 03746?

ZIP code 03746 (Cornish Flat, 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 Cornish Flat, NH?

The median last spring frost (32 °F) near 03746 is May 8; after May 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, N Hartland Lake station.

When is the first frost in Cornish Flat, NH?

The median first fall frost near 03746 is October 6, giving a median frost-free growing season of 150 days.

When should I plant tomatoes in 03746?

Start tomato seeds indoors around Mar 13 – Mar 27 and set transplants outside around May 15 – May 29, one to three weeks after the median last frost.

How much rain and snow does 03746 get?

About 38.1 inches of precipitation a year (NOAA 1991–2020 normals, Lebanon Municipal Airport station).

How hot do summers get in Cornish Flat, 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 03746 have?

The USDA soil survey maps Haven at the center of ZIP 03746: very fine sandy loam, well drained, pH about 5.3 (strongly acidic).

Did spring come early in Cornish Flat, NH in 2026?

Spring leaf-out near 03746 came on Apr 16 in 2026, 4 days earlier than the 1991–2020 average (Apr 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cornish Flat, NH?

Long-day onions: the longest day near 03746 is 15 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).