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

Planting zone for 48028 — Harsens Island, MI

ZIP code 48028 (Harsens Island, St. Clair County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 3 and the first fall frost October 18.

Where ZIP 48028 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostMay 3
First frostOct 18
2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harsens Island, MI…

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 Harsens Island, MI

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 3median — 50% chance of a later frost
Safe for tender plantsMay 23only 10% chance of frost after
First fall frostOctober 18median — 10% chance by Oct 4
Growing season167 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 31.

From the NOAA station Algonac Wwtp, MI — 4 miles away, elevation 581 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 48028

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 22 – Apr 5
SpinachSow outdoors · Mar 22 – Apr 12
Broccoli, cabbageStart indoors · Feb 22 – Mar 8
Broccoli, cabbageTransplant · Apr 12 – Apr 26
Onion setsPlant outdoors · Apr 5 – Apr 19
PotatoesPlant outdoors · Apr 12 – Apr 26
LettuceSow outdoors · Apr 5 – Apr 19
Carrots, beetsSow outdoors · Apr 12 – Apr 26
TomatoesStart indoors · Mar 8 – Mar 22
TomatoesTransplant · May 10 – May 24
Peppers, eggplantStart indoors · Feb 22 – Mar 8
Peppers, eggplantTransplant · May 17 – May 31
BeansSow outdoors · May 10 – May 24
Sweet cornSow outdoors · May 10 – May 24
Cucumbers, squashSow outdoors · May 10 – May 24
Fall lettuce, spinachSow outdoors · Aug 23 – Sep 6
GarlicPlant cloves · Oct 4 – Nov 8
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 3) and first fall frost (Oct 18) 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 48028 came on Apr 5 — 5 days earlier than the 1991–2020 average (Apr 10).

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 6b in Michigan

582 plants native to the lower 48 states, recorded in Michigan, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 58

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 105

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 221

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °F

Grasses 175

alpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fautumn bluegrass1.5 ft · blooms late spring · medium shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 8

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °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 °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 Harsens Island, MI.

Soil in Harsens Island, MI

The soil mapped at the center of ZIP 48028 is Bach — very fine sandy loam, very poorly drained.

TextureVery fine sandy loamdrains and warms fast; dries out and needs more feeding
pH8.0alkaline; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter4%moderate
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Bach very fine sandy 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 48028; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harsens Island, MI

Summer high85 °Faverage high, July
Winter low16 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights137nights a year at 32 °F or less
Growing degree days2,736base 50 °F — the season’s usable heat
Longest day15 h 19 mindaylight on June 21
Shortest day9 h 03 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation34.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 33 °F, low 16 °F 33°16° JanFebruary: average high 35 °F, low 16 °F 35°16° FebMarch: average high 45 °F, low 24 °F 45°24° MarApril: average high 58 °F, low 34 °F 58°34° AprMay: average high 70 °F, low 45 °F 70°45° MayJune: average high 80 °F, low 54 °F 80°54° JunJuly: average high 85 °F, low 60 °F 85°60° JulAugust: average high 83 °F, low 59 °F 83°59° AugSeptember: average high 76 °F, low 51 °F 76°51° SepOctober: average high 63 °F, low 41 °F 63°41° OctNovember: average high 49 °F, low 31 °F 49°31° NovDecember: average high 38 °F, low 23 °F 38°23° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.42 in precipitation 2.4 JanFebruary: 2.06 in precipitation 2.1 FebMarch: 2.16 in precipitation 2.2 MarApril: 3.24 in precipitation 3.2 AprMay: 3.61 in precipitation 3.6 MayJune: 3.36 in precipitation 3.4 JunJuly: 3.40 in precipitation 3.4 JulAugust: 3.24 in precipitation 3.2 AugSeptember: 3.30 in precipitation 3.3 SepOctober: 2.84 in precipitation 2.8 OctNovember: 2.74 in precipitation 2.7 NovDecember: 2.25 in precipitation 2.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Algonac Wwtp, MI (4 mi away); precipitation: Algonac Wwtp, MI (4 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.

480016b
Algonac, MI · 4 mi
480396b
Marine City, MI · 9 mi
480236b
Fair Haven, MI · 9 mi
480456b
Harrison Township, MI · 10 mi
480476b
New Baltimore, MI · 10 mi
480646a
Casco, MI · 13 mi
480516b
New Baltimore, MI · 13 mi
480466b
Mount Clemens, MI · 13 mi

Michigan planting zones →

Questions about 48028

What planting zone is ZIP code 48028?

ZIP code 48028 (Harsens Island, MI) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Harsens Island, MI?

The median last spring frost (32 °F) near 48028 is May 3; after May 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Algonac Wwtp station.

When is the first frost in Harsens Island, MI?

The median first fall frost near 48028 is October 18, giving a median frost-free growing season of 167 days.

When should I plant tomatoes in 48028?

Start tomato seeds indoors around Mar 8 – Mar 22 and set transplants outside around May 10 – May 24, one to three weeks after the median last frost.

How much rain and snow does 48028 get?

About 34.6 inches of precipitation a year (NOAA 1991–2020 normals, Algonac Wwtp station).

How hot do summers get in Harsens Island, MI?

The average high peaks at 85 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 48028 have?

The USDA soil survey maps Bach at the center of ZIP 48028: very fine sandy loam, very poorly drained, pH about 8.0 (alkaline).

Did spring come early in Harsens Island, MI in 2026?

Spring leaf-out near 48028 came on Apr 5 in 2026, 5 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harsens Island, MI?

Long-day onions: the longest day near 48028 is 15 h 19 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 48028 change?

Yes. The 2012 USDA map put 48028 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.