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

Planting zone for 48103 — Ann Arbor, MI

ZIP code 48103 (Ann Arbor, Washtenaw County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 8 and the first fall frost October 4.

Where ZIP 48103 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 frostMay 8
First frostOct 4
2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Ann Arbor, 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 Ann Arbor, MI

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 26only 10% chance of frost after
First fall frostOctober 4median — 10% chance by Sep 20
Growing season147 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 27 and returns around October 16.

From the NOAA station Ann Arbor Municipal Airport, MI — 6 miles away, elevation 840 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 48103

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 9 – Aug 23
GarlicPlant cloves · Sep 20 – Oct 25
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 8) and first fall frost (Oct 4) 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 48103 came on Mar 27 — 14 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 6a in Michigan

580 plants native to the lower 48 states, recorded in Michigan, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 220

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 174

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 °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 °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 Ann Arbor, MI.

Soil in Ann Arbor, MI

The soil mapped at the center of ZIP 48103 is Kibbie — fine sandy loam, somewhat poorly drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH6.7neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Kibbie fine sandy loam, 0 to 4 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 48103; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ann Arbor, MI

Summer high84 °Faverage high, July
Winter low15 °Faverage low, January
Hot days11days a year at 90 °F or more
Freezing nights150nights a year at 32 °F or less
Growing degree days2,545base 50 °F — the season’s usable heat
Longest day15 h 16 mindaylight on June 21
Shortest day9 h 05 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation33.7 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 32 °F, low 15 °F 32°15° JanFebruary: average high 35 °F, low 16 °F 35°16° FebMarch: average high 45 °F, low 25 °F 45°25° MarApril: average high 59 °F, low 35 °F 59°35° AprMay: average high 70 °F, low 46 °F 70°46° MayJune: average high 79 °F, low 54 °F 79°54° JunJuly: average high 84 °F, low 57 °F 84°57° JulAugust: average high 81 °F, low 57 °F 81°57° AugSeptember: average high 74 °F, low 48 °F 74°48° SepOctober: average high 62 °F, low 38 °F 62°38° OctNovember: average high 48 °F, low 30 °F 48°30° NovDecember: average high 36 °F, low 22 °F 36°22° Dec

Precipitation by month inches

0″1″2″3″4″January: 2.47 in precipitation 2.5 JanFebruary: 1.85 in precipitation 1.9 FebMarch: 2.16 in precipitation 2.2 MarApril: 3.20 in precipitation 3.2 AprMay: 3.90 in precipitation 3.9 MayJune: 3.10 in precipitation 3.1 JunJuly: 3.50 in precipitation 3.5 JulAugust: 3.33 in precipitation 3.3 AugSeptember: 2.84 in precipitation 2.8 SepOctober: 2.61 in precipitation 2.6 OctNovember: 2.60 in precipitation 2.6 NovDecember: 2.11 in precipitation 2.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ann Arbor Municipal Airport, MI (6 mi away); precipitation: Ann Arbor 4.5 W, MI (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

481066a
Ann Arbor, MI · <1 mi
481076a
Ann Arbor, MI · <1 mi
481136a
Ann Arbor, MI · <1 mi
481086a
Ann Arbor, MI · 6 mi
481046a
Ann Arbor, MI · 7 mi
481096a
Ann Arbor, MI · 7 mi
481156a
Bridgewater, MI · 8 mi
481306a
Dexter, MI · 8 mi

All 8 ZIP codes in Ann Arbor → · Michigan planting zones →

Questions about 48103

What planting zone is ZIP code 48103?

ZIP code 48103 (Ann Arbor, MI) 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 Ann Arbor, MI?

The median last spring frost (32 °F) near 48103 is May 8; after May 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ann Arbor Municipal Airport station.

When is the first frost in Ann Arbor, MI?

The median first fall frost near 48103 is October 4, giving a median frost-free growing season of 147 days.

When should I plant tomatoes in 48103?

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 48103 get?

About 33.7 inches of precipitation a year (NOAA 1991–2020 normals, Ann Arbor 4.5 W station).

How hot do summers get in Ann Arbor, MI?

The average high peaks at 84 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 48103 have?

The USDA soil survey maps Kibbie at the center of ZIP 48103: fine sandy loam, somewhat poorly drained, pH about 6.7 (neutral).

Did spring come early in Ann Arbor, MI in 2026?

Spring leaf-out near 48103 came on Mar 27 in 2026, 14 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ann Arbor, MI?

Long-day onions: the longest day near 48103 is 15 h 16 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).