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

Planting zone for 01550 — Southbridge, MA

ZIP code 01550 (Southbridge, Worcester County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 25 and the first fall frost October 13.

Where ZIP 01550 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostApr 25
First frostOct 13
2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Southbridge, MA…

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 Southbridge, MA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 25median — 50% chance of a later frost
Safe for tender plantsMay 8only 10% chance of frost after
First fall frostOctober 13median — 10% chance by Oct 2
Growing season168 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 13 and returns around October 25.

From the NOAA station Southbridge 3 Sw, MA — 2 miles away, elevation 686 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 01550

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 14 – Mar 28
SpinachSow outdoors · Mar 14 – Apr 4
Broccoli, cabbageStart indoors · Feb 14 – Feb 28
Broccoli, cabbageTransplant · Apr 4 – Apr 18
Onion setsPlant outdoors · Mar 28 – Apr 11
PotatoesPlant outdoors · Apr 4 – Apr 18
LettuceSow outdoors · Mar 28 – Apr 11
Carrots, beetsSow outdoors · Apr 4 – Apr 18
TomatoesStart indoors · Feb 28 – Mar 14
TomatoesTransplant · May 2 – May 16
Peppers, eggplantStart indoors · Feb 14 – Feb 28
Peppers, eggplantTransplant · May 9 – May 23
BeansSow outdoors · May 2 – May 16
Sweet cornSow outdoors · May 2 – May 16
Cucumbers, squashSow outdoors · May 2 – May 16
Fall lettuce, spinachSow outdoors · Aug 18 – Sep 1
GarlicPlant cloves · Sep 29 – Nov 3
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 13) 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 01550 came on Apr 5 — 7 days earlier than the 1991–2020 average (Apr 12).

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 6b in Massachusetts

548 plants native to the lower 48 states, recorded in Massachusetts, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 66

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 109

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °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 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 188

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 159

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °F

Vines 8

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 Southbridge, MA.

Soil in Southbridge, MA

The soil mapped at the center of ZIP 01550 is Whitman — peat, very poorly drained.

TexturePeattop layer
DrainageVery poorly drainedconsider raised beds
Organic matter95%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Whitman fine sandy loam, 0 to 3 percent slopes, extremely 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 01550; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Southbridge, MA

Summer high81 °Faverage high, July
Winter low17 °Faverage low, January
Hot days6days a year at 90 °F or more
Freezing nights147nights a year at 32 °F or less
Growing degree days2,437base 50 °F — the season’s usable heat
Longest day15 h 15 mindaylight on June 21
Shortest day9 h 06 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation51.9 inper year, rain and melted snow
Snowfall52 inper year; 50 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 35 °F, low 17 °F 35°17° JanFebruary: average high 36 °F, low 18 °F 36°18° FebMarch: average high 45 °F, low 25 °F 45°25° MarApril: average high 58 °F, low 35 °F 58°35° AprMay: average high 69 °F, low 46 °F 69°46° MayJune: average high 77 °F, low 55 °F 77°55° JunJuly: average high 81 °F, low 60 °F 81°60° JulAugust: average high 79 °F, low 59 °F 79°59° AugSeptember: average high 72 °F, low 51 °F 72°51° SepOctober: average high 59 °F, low 39 °F 59°39° OctNovember: average high 49 °F, low 31 °F 49°31° NovDecember: average high 39 °F, low 23 °F 39°23° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 4.05 in precipitation, 14.7 in snowfall 4.0❄15 JanFebruary: 3.52 in precipitation, 14.7 in snowfall 3.5❄15 FebMarch: 4.61 in precipitation, 9.2 in snowfall 4.6❄9 MarApril: 4.44 in precipitation, 1.8 in snowfall 4.4❄2 AprMay: 3.74 in precipitation 3.7 MayJune: 4.39 in precipitation 4.4 JunJuly: 4.33 in precipitation 4.3 JulAugust: 4.44 in precipitation 4.4 AugSeptember: 4.24 in precipitation 4.2 SepOctober: 4.97 in precipitation, 0.2 in snowfall 5.0 OctNovember: 4.10 in precipitation, 1.5 in snowfall 4.1❄2 NovDecember: 5.08 in precipitation, 10.3 in snowfall 5.1❄10 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Southbridge 3 Sw, MA (2 mi away); precipitation: Southbridge 3 Sw, MA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

015666a
Sturbridge, MA · 4 mi
015716b
Dudley, MA · 5 mi
062626a
Quinebaug, CT · 5 mi
015186a
Fiskdale, MA · 5 mi
062456a
Fabyan, CT · 5 mi
062446a
East Woodstock, CT · 6 mi
062816b
Woodstock, CT · 6 mi
015076b
Charlton, MA · 6 mi

Massachusetts planting zones →

Questions about 01550

What planting zone is ZIP code 01550?

ZIP code 01550 (Southbridge, MA) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Southbridge, MA?

The median last spring frost (32 °F) near 01550 is April 25; after May 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Southbridge 3 Sw station.

When is the first frost in Southbridge, MA?

The median first fall frost near 01550 is October 13, giving a median frost-free growing season of 168 days.

When should I plant tomatoes in 01550?

Start tomato seeds indoors around Feb 28 – Mar 14 and set transplants outside around May 2 – May 16, one to three weeks after the median last frost.

How much rain and snow does 01550 get?

About 51.9 inches of precipitation a year and 52 inches of snowfall (NOAA 1991–2020 normals, Southbridge 3 Sw station).

How hot do summers get in Southbridge, MA?

The average high peaks at 81 °F in July, with about 6 days a year at 90 °F or more.

What kind of soil does 01550 have?

The USDA soil survey maps Whitman at the center of ZIP 01550: peat, very poorly drained.

Did spring come early in Southbridge, MA in 2026?

Spring leaf-out near 01550 came on Apr 5 in 2026, 7 days earlier than the 1991–2020 average (Apr 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Southbridge, MA?

Long-day onions: the longest day near 01550 is 15 h 15 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 01550 change?

Yes. The 2012 USDA map put 01550 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.