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

Planting zone for Watertown, WI

Watertown, WI is in USDA zones 5a to 5b across its 2 ZIP codes. The median last spring frost is April 28 and the first fall frost October 12.

Watertown on the zone map

Outlined: its 2 ZIP code areas · 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.

Zones5a–5b−20 to −10 °F
ZIP codes2
Last frostApr 28
First frostOct 12
Growing season167 days

5a 1 ZIP   5b 1 ZIP

Frost forecast — next 7 nights

live from the National Weather Service

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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, WI

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 28median — 50% chance of a later frost
Safe for tender plantsMay 13only 10% chance of frost after
First fall frostOctober 12median — 10% chance by Sep 28
Growing season167 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 16 and returns around October 25.

From the NOAA station Watertown Wwtp, WI, elevation 827 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 Watertown

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 17 – Mar 31
SpinachSow outdoors · Mar 17 – Apr 7
Broccoli, cabbageStart indoors · Feb 17 – Mar 3
Broccoli, cabbageTransplant · Apr 7 – Apr 21
Onion setsPlant outdoors · Mar 31 – Apr 14
PotatoesPlant outdoors · Apr 7 – Apr 21
LettuceSow outdoors · Mar 31 – Apr 14
Carrots, beetsSow outdoors · Apr 7 – Apr 21
TomatoesStart indoors · Mar 3 – Mar 17
TomatoesTransplant · May 5 – May 19
Peppers, eggplantStart indoors · Feb 17 – Mar 3
Peppers, eggplantTransplant · May 12 – May 26
BeansSow outdoors · May 5 – May 19
Sweet cornSow outdoors · May 5 – May 19
Cucumbers, squashSow outdoors · May 5 – May 19
Fall lettuce, spinachSow outdoors · Aug 17 – Aug 31
GarlicPlant cloves · Sep 28 – Nov 2
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 12) 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 53098 came on Mar 30 — 14 days earlier than the 1991–2020 average (Apr 13).

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 Wisconsin

510 plants native to the lower 48 states, recorded in Wisconsin, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. Each links to its USDA PLANTS profile.

Trees 48

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 °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 191

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 158

American 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 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 5

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 °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, WI.

Soil in Watertown, WI

The soil mapped at the center of ZIP 53098 is Elvers — silt loam, very poorly drained.

TextureSilt loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter1.5%low — add compost
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classPrime farmland if drained and either protected from flooding or not frequently flooded during the growing seasonUSDA classification

Map unit: Elvers silt loam.

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 53098; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Watertown, WI

Summer high81 °Faverage high, July
Winter low11 °Faverage low, January
Hot days7days a year at 90 °F or more
Freezing nights149nights a year at 32 °F or less
Growing degree days2,588base 50 °F — the season’s usable heat
Longest day15 h 23 mindaylight on June 21
Shortest day8 h 59 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation35 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 26 °F, low 11 °F 26°11° JanFebruary: average high 30 °F, low 13 °F 30°13° FebMarch: average high 42 °F, low 24 °F 42°24° MarApril: average high 56 °F, low 35 °F 56°35° AprMay: average high 68 °F, low 47 °F 68°47° MayJune: average high 78 °F, low 57 °F 78°57° JunJuly: average high 81 °F, low 61 °F 81°61° JulAugust: average high 80 °F, low 59 °F 80°59° AugSeptember: average high 73 °F, low 51 °F 73°51° SepOctober: average high 60 °F, low 40 °F 60°40° OctNovember: average high 45 °F, low 28 °F 45°28° NovDecember: average high 32 °F, low 17 °F 32°17° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 1.55 in precipitation 1.6 JanFebruary: 1.72 in precipitation 1.7 FebMarch: 1.92 in precipitation 1.9 MarApril: 3.55 in precipitation 3.5 AprMay: 3.70 in precipitation 3.7 MayJune: 5.09 in precipitation 5.1 JunJuly: 4.22 in precipitation 4.2 JulAugust: 3.62 in precipitation 3.6 AugSeptember: 3.06 in precipitation 3.1 SepOctober: 3.02 in precipitation 3.0 OctNovember: 1.95 in precipitation 1.9 NovDecember: 1.63 in precipitation 1.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Watertown Wwtp, WI (6 mi away); precipitation: Clyman, WI (4 mi away). Daylight is calculated from latitude.

ZIP codes in Watertown

530945b
−15 to −10 °F
530985a
−20 to −15 °F

Wisconsin planting zones →

Questions about Watertown

What planting zone is Watertown, WI?

Watertown, WI is in USDA hardiness zones 5a to 5b on the 2023 map (5a: −20 to −15 °F; 5b: −15 to −10 °F).

When is the last frost in Watertown, WI?

The median last spring frost is April 28 and the median first fall frost is October 12 (NOAA 1991–2020 normals, Watertown Wwtp station).

When can I plant a garden in Watertown, WI?

Cool-season crops like peas and spinach go in around Mar 17 – Apr 7; tomatoes, peppers, beans and squash after about May 5, once frost risk has passed.

What kind of onions grow in Watertown, WI?

Long-day onions: the longest day is 15 h 23 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Watertown, WI get?

About 35 inches of precipitation a year (NOAA 1991–2020 normals).