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

Planting zone for 03589 — Mount Washington, NH

ZIP code 03589 (Mount Washington, Coos County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 19 and the first fall frost September 29.

Where ZIP 03589 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.

Zone4a−30 to −25 °F
Coldest night−34.4 to −31.7 °C
Last frostMay 19
First frostSep 29
2012 zone4b

Was 4b on the 2012 map — half a zone colder now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Washington, 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 Mount Washington, NH

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 19median — 50% chance of a later frost
Safe for tender plantsJune 2only 10% chance of frost after
First fall frostSeptember 29median — 10% chance by Sep 15
Growing season131 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 4 and returns around October 7.

From the NOAA station N Stratford, NH — 10 miles away, elevation 951 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 03589

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 7 – Apr 21
SpinachSow outdoors · Apr 7 – Apr 28
Broccoli, cabbageStart indoors · Mar 10 – Mar 24
Broccoli, cabbageTransplant · Apr 28 – May 12
Onion setsPlant outdoors · Apr 21 – May 5
PotatoesPlant outdoors · Apr 28 – May 12
LettuceSow outdoors · Apr 21 – May 5
Carrots, beetsSow outdoors · Apr 28 – May 12
TomatoesStart indoors · Mar 24 – Apr 7
TomatoesTransplant · May 26 – Jun 9
Peppers, eggplantStart indoors · Mar 10 – Mar 24
Peppers, eggplantTransplant · Jun 2 – Jun 16
BeansSow outdoors · May 26 – Jun 9
Sweet cornSow outdoors · May 26 – Jun 9
Cucumbers, squashSow outdoors · May 26 – Jun 9
Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18
GarlicPlant cloves · Sep 15 – Oct 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 19) and first fall frost (Sep 29) 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 03589 came on May 1 — 4 days earlier than the 1991–2020 average (May 5).

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 Mount Washington, NH

The soil mapped at the center of ZIP 03589 is Saddleback — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH4.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter85%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Saddleback-Glebe-Ricker association, steep, 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 03589; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Washington, NH

Summer high79 °Faverage high, July
Winter low2 °Faverage low, January
Hot days2days a year at 90 °F or more
Freezing nights186nights a year at 32 °F or less
Growing degree days1,851base 50 °F — the season’s usable heat
Longest day15 h 35 mindaylight on June 21
Shortest day8 h 48 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.6 inper year, rain and melted snow
Snowfall79 inper year; 116 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 25 °F, low 2 °F 25°2° JanFebruary: average high 28 °F, low 2 °F 28°2° FebMarch: average high 37 °F, low 14 °F 37°14° MarApril: average high 52 °F, low 29 °F 52°29° AprMay: average high 66 °F, low 40 °F 66°40° MayJune: average high 74 °F, low 50 °F 74°50° JunJuly: average high 79 °F, low 55 °F 79°55° JulAugust: average high 77 °F, low 53 °F 77°53° AugSeptember: average high 70 °F, low 45 °F 70°45° SepOctober: average high 56 °F, low 34 °F 56°34° OctNovember: average high 42 °F, low 24 °F 42°24° NovDecember: average high 31 °F, low 12 °F 31°12° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 2.55 in precipitation, 16.9 in snowfall 2.5❄17 JanFebruary: 2.24 in precipitation, 19.9 in snowfall 2.2❄20 FebMarch: 2.42 in precipitation, 13.9 in snowfall 2.4❄14 MarApril: 3.02 in precipitation, 5.3 in snowfall 3.0❄5 AprMay: 3.70 in precipitation, 0.1 in snowfall 3.7 MayJune: 4.39 in precipitation 4.4 JunJuly: 4.54 in precipitation 4.5 JulAugust: 3.98 in precipitation 4.0 AugSeptember: 3.60 in precipitation 3.6 SepOctober: 4.21 in precipitation, 0.4 in snowfall 4.2 OctNovember: 2.92 in precipitation, 5.2 in snowfall 2.9❄5 NovDecember: 3.04 in precipitation, 17.4 in snowfall 3.0❄17 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: N Stratford, NH (10 mi away); precipitation: N Stratford, NH (10 mi away). 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.

035974a
West Stewartstown, NH · 3 mi
035904a
North Stratford, NH · 7 mi
035824b
Groveton, NH · 9 mi
035884b
Milan, NH · 10 mi
035764a
Colebrook, NH · 14 mi
059054a
Guildhall, VT · 14 mi
035704b
Berlin, NH · 16 mi
035844b
Lancaster, NH · 16 mi

New Hampshire planting zones →

Questions about 03589

What planting zone is ZIP code 03589?

ZIP code 03589 (Mount Washington, NH) is in USDA hardiness zone 4a on the 2023 map: the coldest night of an average winter reaches −30 to −25 °F (−34.4 to −31.7 °C).

When is the last frost in Mount Washington, NH?

The median last spring frost (32 °F) near 03589 is May 19; after June 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, N Stratford station.

When is the first frost in Mount Washington, NH?

The median first fall frost near 03589 is September 29, giving a median frost-free growing season of 131 days.

When should I plant tomatoes in 03589?

Start tomato seeds indoors around Mar 24 – Apr 7 and set transplants outside around May 26 – Jun 9, one to three weeks after the median last frost.

How much rain and snow does 03589 get?

About 40.6 inches of precipitation a year and 79 inches of snowfall (NOAA 1991–2020 normals, N Stratford station).

How hot do summers get in Mount Washington, NH?

The average high peaks at 79 °F in July, with about 2 days a year at 90 °F or more.

What kind of soil does 03589 have?

The USDA soil survey maps Saddleback at the center of ZIP 03589: slightly decomposed plant material, well drained, pH about 4.0 (strongly acidic).

Did spring come early in Mount Washington, NH in 2026?

Spring leaf-out near 03589 came on May 1 in 2026, 4 days earlier than the 1991–2020 average (May 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Washington, NH?

Long-day onions: the longest day near 03589 is 15 h 35 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 03589 change?

Yes. The 2012 USDA map put 03589 in zone 4b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.