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

Planting zone for 55388 — Watertown, MN

ZIP code 55388 (Watertown, Carver County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is April 30 and the first fall frost October 8.

Where ZIP 55388 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostApr 30
First frostOct 8
2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Watertown, MN…

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 Watertown, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 30median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 8median — 10% chance by Sep 24
Growing season159 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 19.

From the NOAA station Delano, MN — 7 miles away, elevation 974 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 55388

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 19 – Apr 2
SpinachSow outdoors · Mar 19 – Apr 9
Broccoli, cabbageStart indoors · Feb 19 – Mar 5
Broccoli, cabbageTransplant · Apr 9 – Apr 23
Onion setsPlant outdoors · Apr 2 – Apr 16
PotatoesPlant outdoors · Apr 9 – Apr 23
LettuceSow outdoors · Apr 2 – Apr 16
Carrots, beetsSow outdoors · Apr 9 – Apr 23
TomatoesStart indoors · Mar 5 – Mar 19
TomatoesTransplant · May 7 – May 21
Peppers, eggplantStart indoors · Feb 19 – Mar 5
Peppers, eggplantTransplant · May 14 – May 28
BeansSow outdoors · May 7 – May 21
Sweet cornSow outdoors · May 7 – May 21
Cucumbers, squashSow outdoors · May 7 – May 21
Fall lettuce, spinachSow outdoors · Aug 13 – Aug 27
GarlicPlant cloves · Sep 24 – Oct 29
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 30) and first fall frost (Oct 8) 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 55388 came on Apr 11 — 6 days earlier than the 1991–2020 average (Apr 17).

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 4b in Minnesota

497 plants native to the lower 48 states, recorded in Minnesota, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 47

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °F

Shrubs 88

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 hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 190

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high 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 °F

Grasses 156

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °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 °Fbasin wildrye5 ft · blooms early spring · high shade tolerance · to −43 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 4

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 °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 Watertown, MN.

Soil in Watertown, MN

The soil mapped at the center of ZIP 55388 is Hanlon — fine sandy loam, moderately well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH6.7neutral; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Hanlon-Kalmarville complex, frequently flooded.

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 55388; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Watertown, MN

Summer high83 °Faverage high, July
Winter low4 °Faverage low, January
Hot days8days a year at 90 °F or more
Freezing nights166nights a year at 32 °F or less
Growing degree days2,592base 50 °F — the season’s usable heat
Longest day15 h 37 mindaylight on June 21
Shortest day8 h 46 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation30.8 inper year, rain and melted snow

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 23 °F, low 4 °F 23°4° JanFebruary: average high 28 °F, low 7 °F 28°7° FebMarch: average high 40 °F, low 21 °F 40°21° MarApril: average high 56 °F, low 33 °F 56°33° AprMay: average high 69 °F, low 47 °F 69°47° MayJune: average high 78 °F, low 57 °F 78°57° JunJuly: average high 83 °F, low 62 °F 83°62° JulAugust: average high 80 °F, low 59 °F 80°59° AugSeptember: average high 72 °F, low 50 °F 72°50° SepOctober: average high 58 °F, low 37 °F 58°37° OctNovember: average high 41 °F, low 24 °F 41°24° NovDecember: average high 28 °F, low 12 °F 28°12° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 0.69 in precipitation 0.7 JanFebruary: 0.81 in precipitation 0.8 FebMarch: 1.43 in precipitation 1.4 MarApril: 2.68 in precipitation 2.7 AprMay: 4.32 in precipitation 4.3 MayJune: 4.46 in precipitation 4.5 JunJuly: 3.94 in precipitation 3.9 JulAugust: 4.16 in precipitation 4.2 AugSeptember: 3.21 in precipitation 3.2 SepOctober: 2.55 in precipitation 2.5 OctNovember: 1.50 in precipitation 1.5 NovDecember: 1.05 in precipitation 1.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Delano, MN (7 mi away); precipitation: Minnetrista 1.5 Sse, MN (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

553604b
Mayer, MN · 4 mi
553284b
Delano, MN · 6 mi
553634b
Montrose, MN · 7 mi
553874b
Waconia, MN · 7 mi
553754b
Saint Bonifacius, MN · 7 mi
553674b
New Germany, MN · 7 mi
553594b
Maple Plain, MN · 8 mi
553644b
Mound, MN · 9 mi

Minnesota planting zones →

Questions about 55388

What planting zone is ZIP code 55388?

ZIP code 55388 (Watertown, MN) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Watertown, MN?

The median last spring frost (32 °F) near 55388 is April 30; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Delano station.

When is the first frost in Watertown, MN?

The median first fall frost near 55388 is October 8, giving a median frost-free growing season of 159 days.

When should I plant tomatoes in 55388?

Start tomato seeds indoors around Mar 5 – Mar 19 and set transplants outside around May 7 – May 21, one to three weeks after the median last frost.

How much rain and snow does 55388 get?

About 30.8 inches of precipitation a year (NOAA 1991–2020 normals, Minnetrista 1.5 Sse station).

How hot do summers get in Watertown, MN?

The average high peaks at 83 °F in July, with about 8 days a year at 90 °F or more.

What kind of soil does 55388 have?

The USDA soil survey maps Hanlon at the center of ZIP 55388: fine sandy loam, moderately well drained, pH about 6.7 (neutral).

Did spring come early in Watertown, MN in 2026?

Spring leaf-out near 55388 came on Apr 11 in 2026, 6 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Watertown, MN?

Long-day onions: the longest day near 55388 is 15 h 37 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).