Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 03887 — Union, NH

ZIP code 03887 (Union, Strafford County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 16 and the first fall frost September 30.

Where ZIP 03887 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 16

First frostSep 30

2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Union, 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 Union, NH

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 16median — 50% chance of a later frost

Safe for tender plantsMay 29only 10% chance of frost after

First fall frostSeptember 30median — 10% chance by Sep 18

Growing season136 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 7.

From the NOAA station Sanford 2 Nnw, ME — 15 miles away, elevation 289 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 03887

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 4 – Apr 18

SpinachSow outdoors · Apr 4 – Apr 25

Broccoli, cabbageStart indoors · Mar 7 – Mar 21

Broccoli, cabbageTransplant · Apr 25 – May 9

Onion setsPlant outdoors · Apr 18 – May 2

PotatoesPlant outdoors · Apr 25 – May 9

LettuceSow outdoors · Apr 18 – May 2

Carrots, beetsSow outdoors · Apr 25 – May 9

TomatoesStart indoors · Mar 21 – Apr 4

TomatoesTransplant · May 23 – Jun 6

Peppers, eggplantStart indoors · Mar 7 – Mar 21

Peppers, eggplantTransplant · May 30 – Jun 13

BeansSow outdoors · May 23 – Jun 6

Sweet cornSow outdoors · May 23 – Jun 6

Cucumbers, squashSow outdoors · May 23 – Jun 6

Fall lettuce, spinachSow outdoors · Aug 5 – Aug 19

GarlicPlant cloves · Sep 16 – Oct 21

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 16) and first fall frost (Sep 30) 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 03887 came on Apr 16 — 4 days earlier than the 1991–2020 average (Apr 20).

average
Apr 202026
Apr 16

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.

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 Union, NH.

Soil in Union, NH

The soil mapped at the center of ZIP 03887 is Gloucester — very stony fine sandy loam, somewhat excessively drained.

TextureVery stony fine sandy loamdrains and warms fast; dries out and needs more feeding

pH4.8strongly acidic; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter1.35%low — add compost

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Gloucester very stony 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 03887; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Union, NH

Summer high81 °Faverage high, July

Winter low10 °Faverage low, January

Hot days10days a year at 90 °F or more

Freezing nights156nights a year at 32 °F or less

Growing degree days2,120base 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)

Precipitation53 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Sanford 2 Nnw, ME (15 mi away); precipitation: East Wakefield 1.2 Se, NH (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

038515b

Milton, NH · 4 mi

038555b

New Durham, NH · 4 mi

038525b

Milton Mills, NH · 4 mi

038725b

Sanbornville, NH · 6 mi

Farmington, NH · 8 mi

040275b

Lebanon, ME · 10 mi

New Hampshire planting zones →

Questions about 03887

What planting zone is ZIP code 03887?

ZIP code 03887 (Union, 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 Union, NH?

The median last spring frost (32 °F) near 03887 is May 16; after May 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sanford 2 Nnw station.

When is the first frost in Union, NH?

The median first fall frost near 03887 is September 30, giving a median frost-free growing season of 136 days.

When should I plant tomatoes in 03887?

Start tomato seeds indoors around Mar 21 – Apr 4 and set transplants outside around May 23 – Jun 6, one to three weeks after the median last frost.

How much rain and snow does 03887 get?

About 53 inches of precipitation a year (NOAA 1991–2020 normals, East Wakefield 1.2 Se station).

How hot do summers get in Union, NH?

The average high peaks at 81 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 03887 have?

The USDA soil survey maps Gloucester at the center of ZIP 03887: very stony fine sandy loam, somewhat excessively drained, pH about 4.8 (strongly acidic).

Did spring come early in Union, NH in 2026?

Spring leaf-out near 03887 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 Union, NH?

Long-day onions: the longest day near 03887 is 15 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 03887 change?

Yes. The 2012 USDA map put 03887 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.