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

Planting zone for 53172 — South Milwaukee, WI

ZIP code 53172 (South Milwaukee, Milwaukee County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 22 and the first fall frost October 26.

Where ZIP 53172 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostApr 22
First frostOct 26
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for South Milwaukee, WI…

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 South Milwaukee, WI

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 22median — 50% chance of a later frost
Safe for tender plantsMay 8only 10% chance of frost after
First fall frostOctober 26median — 10% chance by Oct 10
Growing season184 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 9 and returns around November 5.

From the NOAA station South Milwaukee Wwtp, WI — within 1 mile, elevation 650 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 53172

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 11 – Mar 25
SpinachSow outdoors · Mar 11 – Apr 1
Broccoli, cabbageStart indoors · Feb 11 – Feb 25
Broccoli, cabbageTransplant · Apr 1 – Apr 15
Onion setsPlant outdoors · Mar 25 – Apr 8
PotatoesPlant outdoors · Apr 1 – Apr 15
LettuceSow outdoors · Mar 25 – Apr 8
Carrots, beetsSow outdoors · Apr 1 – Apr 15
TomatoesStart indoors · Feb 25 – Mar 11
TomatoesTransplant · Apr 29 – May 13
Peppers, eggplantStart indoors · Feb 11 – Feb 25
Peppers, eggplantTransplant · May 6 – May 20
BeansSow outdoors · Apr 29 – May 13
Sweet cornSow outdoors · Apr 29 – May 13
Cucumbers, squashSow outdoors · Apr 29 – May 13
Fall lettuce, spinachSow outdoors · Aug 31 – Sep 14
GarlicPlant cloves · Oct 12 – Nov 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 22) and first fall frost (Oct 26) 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 53172 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 6a in Wisconsin

526 plants native to the lower 48 states, recorded in Wisconsin, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 49

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 94

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 200

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 161

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 6

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 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 South Milwaukee, WI.

Soil in South Milwaukee, WI

The soil mapped at the center of ZIP 53172 is Ozaukee — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.2slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Ozaukee silt loam, 2 to 6 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 53172; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South Milwaukee, WI

Summer high80 °Faverage high, July
Winter low16 °Faverage low, January
Hot days7days a year at 90 °F or more
Freezing nights124nights a year at 32 °F or less
Growing degree days2,716base 50 °F — the season’s usable heat
Longest day15 h 21 mindaylight on June 21
Shortest day9 h 01 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation36.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 30 °F, low 16 °F 30°16° JanFebruary: average high 33 °F, low 18 °F 33°18° FebMarch: average high 42 °F, low 28 °F 42°28° MarApril: average high 53 °F, low 37 °F 53°37° AprMay: average high 64 °F, low 47 °F 64°47° MayJune: average high 75 °F, low 57 °F 75°57° JunJuly: average high 80 °F, low 65 °F 80°65° JulAugust: average high 79 °F, low 64 °F 79°64° AugSeptember: average high 73 °F, low 56 °F 73°56° SepOctober: average high 61 °F, low 44 °F 61°44° OctNovember: average high 48 °F, low 33 °F 48°33° NovDecember: average high 36 °F, low 22 °F 36°22° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 1.65 in precipitation 1.6 JanFebruary: 1.84 in precipitation 1.8 FebMarch: 2.20 in precipitation 2.2 MarApril: 4.08 in precipitation 4.1 AprMay: 4.18 in precipitation 4.2 MayJune: 4.58 in precipitation 4.6 JunJuly: 3.51 in precipitation 3.5 JulAugust: 3.80 in precipitation 3.8 AugSeptember: 3.30 in precipitation 3.3 SepOctober: 3.40 in precipitation 3.4 OctNovember: 2.14 in precipitation 2.1 NovDecember: 1.90 in precipitation 1.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: South Milwaukee Wwtp, WI (within 1 mile); precipitation: South Milwaukee Wwtp, WI (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

531106a
Cudahy, WI · 3 mi
531546a
Oak Creek, WI · 3 mi
532356a
Saint Francis, WI · 4 mi
532076a
Milwaukee, WI · 5 mi
532216a
Milwaukee, WI · 5 mi
532156a
Milwaukee, WI · 7 mi
531295b
Greendale, WI · 7 mi
532205b
Milwaukee, WI · 8 mi

Wisconsin planting zones →

Questions about 53172

What planting zone is ZIP code 53172?

ZIP code 53172 (South Milwaukee, WI) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in South Milwaukee, WI?

The median last spring frost (32 °F) near 53172 is April 22; after May 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, South Milwaukee Wwtp station.

When is the first frost in South Milwaukee, WI?

The median first fall frost near 53172 is October 26, giving a median frost-free growing season of 184 days.

When should I plant tomatoes in 53172?

Start tomato seeds indoors around Feb 25 – Mar 11 and set transplants outside around Apr 29 – May 13, one to three weeks after the median last frost.

How much rain and snow does 53172 get?

About 36.6 inches of precipitation a year (NOAA 1991–2020 normals, South Milwaukee Wwtp station).

How hot do summers get in South Milwaukee, WI?

The average high peaks at 80 °F in July, with about 7 days a year at 90 °F or more.

What kind of soil does 53172 have?

The USDA soil survey maps Ozaukee at the center of ZIP 53172: silt loam, moderately well drained, pH about 6.2 (slightly acidic).

Did spring come early in South Milwaukee, WI in 2026?

Spring leaf-out near 53172 came on Mar 30 in 2026, 14 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in South Milwaukee, WI?

Long-day onions: the longest day near 53172 is 15 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 53172 change?

Yes. The 2012 USDA map put 53172 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.