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

Planting zone for 53027 — Hartford, WI

ZIP code 53027 (Hartford, Washington County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 8 and the first fall frost October 3.

Where ZIP 53027 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 8
First frostOct 3
2012 zone5a

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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Hartford, 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 Hartford, WI

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 8median — 50% chance of a later frost
Safe for tender plantsMay 24only 10% chance of frost after
First fall frostOctober 3median — 10% chance by Sep 20
Growing season148 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 27 and returns around October 15.

From the NOAA station Hartford Wwtp, WI — 2 miles away, elevation 961 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 53027

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 27 – Apr 10
SpinachSow outdoors · Mar 27 – Apr 17
Broccoli, cabbageStart indoors · Feb 27 – Mar 13
Broccoli, cabbageTransplant · Apr 17 – May 1
Onion setsPlant outdoors · Apr 10 – Apr 24
PotatoesPlant outdoors · Apr 17 – May 1
LettuceSow outdoors · Apr 10 – Apr 24
Carrots, beetsSow outdoors · Apr 17 – May 1
TomatoesStart indoors · Mar 13 – Mar 27
TomatoesTransplant · May 15 – May 29
Peppers, eggplantStart indoors · Feb 27 – Mar 13
Peppers, eggplantTransplant · May 22 – Jun 5
BeansSow outdoors · May 15 – May 29
Sweet cornSow outdoors · May 15 – May 29
Cucumbers, squashSow outdoors · May 15 – May 29
Fall lettuce, spinachSow outdoors · Aug 8 – Aug 22
GarlicPlant cloves · Sep 19 – Oct 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 8) and first fall frost (Oct 3) 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 53027 came on Apr 5 — 11 days earlier than the 1991–2020 average (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 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 Hartford, WI.

Soil in Hartford, WI

The soil mapped at the center of ZIP 53027 is Theresa — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH7.0neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Theresa 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 53027; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Hartford, WI

Summer high80 °Faverage high, July
Winter low9 °Faverage low, January
Hot days7days a year at 90 °F or more
Freezing nights159nights a year at 32 °F or less
Growing degree days2,284base 50 °F — the season’s usable heat
Longest day15 h 24 mindaylight on June 21
Shortest day8 h 58 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation34.1 inper year, rain and melted snow
Snowfall36 inper year; 74 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 26 °F, low 9 °F 26°9° JanFebruary: average high 30 °F, low 11 °F 30°11° FebMarch: average high 41 °F, low 22 °F 41°22° MarApril: average high 54 °F, low 33 °F 54°33° AprMay: average high 67 °F, low 44 °F 67°44° MayJune: average high 77 °F, low 54 °F 77°54° JunJuly: average high 80 °F, low 58 °F 80°58° JulAugust: average high 79 °F, low 56 °F 79°56° AugSeptember: average high 72 °F, low 48 °F 72°48° SepOctober: average high 59 °F, low 37 °F 59°37° OctNovember: average high 44 °F, low 26 °F 44°26° NovDecember: average high 31 °F, low 15 °F 31°15° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 1.52 in precipitation, 10 in snowfall 1.5❄10 JanFebruary: 1.26 in precipitation, 9.1 in snowfall 1.3❄9 FebMarch: 1.78 in precipitation, 4 in snowfall 1.8❄4 MarApril: 3.43 in precipitation, 1.4 in snowfall 3.4❄1 AprMay: 3.82 in precipitation, 0.3 in snowfall 3.8 MayJune: 4.77 in precipitation 4.8 JunJuly: 3.89 in precipitation 3.9 JulAugust: 3.74 in precipitation 3.7 AugSeptember: 3.23 in precipitation 3.2 SepOctober: 2.91 in precipitation, 0.3 in snowfall 2.9 OctNovember: 2.06 in precipitation, 1.1 in snowfall 2.1❄1 NovDecember: 1.68 in precipitation, 10.1 in snowfall 1.7❄10 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hartford Wwtp, WI (2 mi away); precipitation: Hartford Wwtp, WI (2 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.

530785a
Rubicon, WI · 5 mi
530865a
Slinger, WI · 5 mi
530335a
Hubertus, WI · 8 mi
530595a
Neosho, WI · 8 mi
530765b
Richfield, WI · 9 mi
530995a
Woodland, WI · 9 mi
530175a
Colgate, WI · 10 mi
530355a
Iron Ridge, WI · 10 mi

Wisconsin planting zones →

Questions about 53027

What planting zone is ZIP code 53027?

ZIP code 53027 (Hartford, WI) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Hartford, WI?

The median last spring frost (32 °F) near 53027 is May 8; after May 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hartford Wwtp station.

When is the first frost in Hartford, WI?

The median first fall frost near 53027 is October 3, giving a median frost-free growing season of 148 days.

When should I plant tomatoes in 53027?

Start tomato seeds indoors around Mar 13 – Mar 27 and set transplants outside around May 15 – May 29, one to three weeks after the median last frost.

How much rain and snow does 53027 get?

About 34.1 inches of precipitation a year and 36 inches of snowfall (NOAA 1991–2020 normals, Hartford Wwtp station).

How hot do summers get in Hartford, 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 53027 have?

The USDA soil survey maps Theresa at the center of ZIP 53027: silt loam, well drained, pH about 7.0 (neutral).

Did spring come early in Hartford, WI in 2026?

Spring leaf-out near 53027 came on Apr 5 in 2026, 11 days earlier than the 1991–2020 average (Apr 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Hartford, WI?

Long-day onions: the longest day near 53027 is 15 h 24 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).