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

Planting zone for 54547 — Mercer, WI

ZIP code 54547 (Mercer, Iron County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 25 and the first fall frost September 21.

Where ZIP 54547 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.

Zone4a−30 to −25 °F
Coldest night−34.4 to −31.7 °C
Last frostMay 25
First frostSep 21
2012 zone4a

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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mercer, 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 Mercer, WI

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 25median — 50% chance of a later frost
Safe for tender plantsJune 9only 10% chance of frost after
First fall frostSeptember 21median — 10% chance by Sep 3
Growing season117 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 11 and returns around October 1.

From the NOAA station Rest Lake, WI — 12 miles away, elevation 1,611 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 54547

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 13 – Apr 27
SpinachSow outdoors · Apr 13 – May 4
Broccoli, cabbageStart indoors · Mar 16 – Mar 30
Broccoli, cabbageTransplant · May 4 – May 18
Onion setsPlant outdoors · Apr 27 – May 11
PotatoesPlant outdoors · May 4 – May 18
LettuceSow outdoors · Apr 27 – May 11
Carrots, beetsSow outdoors · May 4 – May 18
TomatoesStart indoors · Mar 30 – Apr 13
TomatoesTransplant · Jun 1 – Jun 15
Peppers, eggplantStart indoors · Mar 16 – Mar 30
Peppers, eggplantTransplant · Jun 8 – Jun 22
BeansSow outdoors · Jun 1 – Jun 15
Sweet cornSow outdoors · Jun 1 – Jun 15
Cucumbers, squashSow outdoors · Jun 1 – Jun 15
Fall lettuce, spinachSow outdoors · Jul 27 – Aug 10
GarlicPlant cloves · Sep 7 – Oct 12
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 25) and first fall frost (Sep 21) 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 54547 came on Apr 24 — 3 days earlier than the 1991–2020 average (Apr 27).

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 4a in Wisconsin

419 plants native to the lower 48 states, recorded in Wisconsin, and rated by the USDA to survive −30 °F or colder — the bottom of zone 4a. Each links to its USDA PLANTS profile.

Trees 45

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 71

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 157

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 133

arctic 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 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °FBicknell's sedge3 ft · blooms late spring · low shade tolerance · to −38 °Fbig bluestem6 ft · blooms summer · high shade tolerance · to −46 °F

Vines 3

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 °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 Mercer, WI.

Soil in Mercer, WI

The soil mapped at the center of ZIP 54547 is Lupton — muck, very poorly drained.

TextureMucktop layer
pH6.5neutral; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter75%high
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Lupton-Pleine-Cathro complex, 0 to 1 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 54547; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mercer, WI

Summer high78 °Faverage high, July
Winter low0 °Faverage low, January
Hot days3days a year at 90 °F or more
Freezing nights195nights a year at 32 °F or less
Growing degree days1,769base 50 °F — the season’s usable heat
Longest day15 h 47 mindaylight on June 21
Shortest day8 h 37 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation32.3 inper year, rain and melted snow
Snowfall75 inper year; 120 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 20 °F, low 0 °F 20°0° JanFebruary: average high 25 °F, low 3 °F 25°3° FebMarch: average high 37 °F, low 14 °F 37°14° MarApril: average high 50 °F, low 27 °F 50°27° AprMay: average high 65 °F, low 41 °F 65°41° MayJune: average high 74 °F, low 51 °F 74°51° JunJuly: average high 78 °F, low 54 °F 78°54° JulAugust: average high 76 °F, low 53 °F 76°53° AugSeptember: average high 67 °F, low 45 °F 67°45° SepOctober: average high 53 °F, low 33 °F 53°33° OctNovember: average high 37 °F, low 22 °F 37°22° NovDecember: average high 25 °F, low 9 °F 25°9° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 1.21 in precipitation, 16.7 in snowfall 1.2❄17 JanFebruary: 0.93 in precipitation, 12.7 in snowfall 0.9❄13 FebMarch: 1.50 in precipitation, 10.9 in snowfall 1.5❄11 MarApril: 2.54 in precipitation, 7.2 in snowfall 2.5❄7 AprMay: 3.69 in precipitation, 0.3 in snowfall 3.7 MayJune: 4.38 in precipitation 4.4 JunJuly: 4.13 in precipitation 4.1 JulAugust: 3.30 in precipitation 3.3 AugSeptember: 3.66 in precipitation, 0.1 in snowfall 3.7 SepOctober: 3.57 in precipitation, 2.9 in snowfall 3.6❄3 OctNovember: 1.93 in precipitation, 9.1 in snowfall 1.9❄9 NovDecember: 1.42 in precipitation, 15.3 in snowfall 1.4❄15 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Rest Lake, WI (12 mi away); precipitation: Rest Lake, WI (12 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.

545344a
Hurley, WI · 11 mi
545504a
Montreal, WI · 12 mi
545454a
Manitowish Waters, WI · 13 mi
545364a
Iron Belt, WI · 15 mi
545254b
Gile, WI · 16 mi
545654a
Upson, WI · 18 mi
545384a
Lac Du Flambeau, WI · 18 mi
499594a
Ramsay, MI · 19 mi

Wisconsin planting zones →

Questions about 54547

What planting zone is ZIP code 54547?

ZIP code 54547 (Mercer, WI) is in USDA hardiness zone 4a on the 2023 map: the coldest night of an average winter reaches −30 to −25 °F (−34.4 to −31.7 °C).

When is the last frost in Mercer, WI?

The median last spring frost (32 °F) near 54547 is May 25; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Rest Lake station.

When is the first frost in Mercer, WI?

The median first fall frost near 54547 is September 21, giving a median frost-free growing season of 117 days.

When should I plant tomatoes in 54547?

Start tomato seeds indoors around Mar 30 – Apr 13 and set transplants outside around Jun 1 – Jun 15, one to three weeks after the median last frost.

How much rain and snow does 54547 get?

About 32.3 inches of precipitation a year and 75 inches of snowfall (NOAA 1991–2020 normals, Rest Lake station).

How hot do summers get in Mercer, WI?

The average high peaks at 78 °F in July, with about 3 days a year at 90 °F or more.

What kind of soil does 54547 have?

The USDA soil survey maps Lupton at the center of ZIP 54547: muck, very poorly drained, pH about 6.5 (neutral).

Did spring come early in Mercer, WI in 2026?

Spring leaf-out near 54547 came on Apr 24 in 2026, 3 days earlier than the 1991–2020 average (Apr 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mercer, WI?

Long-day onions: the longest day near 54547 is 15 h 47 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).