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

Planting zone for 55398 — Zimmerman, MN

ZIP code 55398 (Zimmerman, Sherburne County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 7 and the first fall frost September 28.

Where ZIP 55398 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostMay 7
First frostSep 28
2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Zimmerman, MN…

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 Zimmerman, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 7median — 50% chance of a later frost
Safe for tender plantsMay 22only 10% chance of frost after
First fall frostSeptember 28median — 10% chance by Sep 15
Growing season144 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 28 and returns around October 8.

From the NOAA station Santiago 3 E, MN — 10 miles away, elevation 1,011 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 55398

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 26 – Apr 9
SpinachSow outdoors · Mar 26 – Apr 16
Broccoli, cabbageStart indoors · Feb 26 – Mar 12
Broccoli, cabbageTransplant · Apr 16 – Apr 30
Onion setsPlant outdoors · Apr 9 – Apr 23
PotatoesPlant outdoors · Apr 16 – Apr 30
LettuceSow outdoors · Apr 9 – Apr 23
Carrots, beetsSow outdoors · Apr 16 – Apr 30
TomatoesStart indoors · Mar 12 – Mar 26
TomatoesTransplant · May 14 – May 28
Peppers, eggplantStart indoors · Feb 26 – Mar 12
Peppers, eggplantTransplant · May 21 – Jun 4
BeansSow outdoors · May 14 – May 28
Sweet cornSow outdoors · May 14 – May 28
Cucumbers, squashSow outdoors · May 14 – May 28
Fall lettuce, spinachSow outdoors · Aug 3 – Aug 17
GarlicPlant cloves · Sep 14 – Oct 19
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 7) and first fall frost (Sep 28) 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 55398 came on Apr 15 — 4 days earlier than the 1991–2020 average (Apr 19).

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 4b in Minnesota

497 plants native to the lower 48 states, recorded in Minnesota, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 47

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °F

Shrubs 88

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 190

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high 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 °F

Grasses 156

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °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 °Fbasin wildrye5 ft · blooms early spring · high shade tolerance · to −43 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 4

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 °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 Zimmerman, MN.

Soil in Zimmerman, MN

The soil mapped at the center of ZIP 55398 is Isanti — loamy fine sand, poorly drained.

TextureLoamy fine sanddrains and warms fast; dries out and needs more feeding
pH6.2slightly acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter9%high
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Isanti loamy fine sand, 0 to 2 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 55398; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Zimmerman, MN

Summer high81 °Faverage high, July
Winter low4 °Faverage low, January
Hot days7days a year at 90 °F or more
Freezing nights170nights a year at 32 °F or less
Growing degree days2,365base 50 °F — the season’s usable heat
Longest day15 h 41 mindaylight on June 21
Shortest day8 h 42 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation31 inper year, rain and melted snow

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 22 °F, low 4 °F 22°4° JanFebruary: average high 27 °F, low 8 °F 27°8° FebMarch: average high 40 °F, low 21 °F 40°21° MarApril: average high 56 °F, low 33 °F 56°33° AprMay: average high 69 °F, low 45 °F 69°45° MayJune: average high 77 °F, low 55 °F 77°55° JunJuly: average high 81 °F, low 59 °F 81°59° JulAugust: average high 79 °F, low 57 °F 79°57° AugSeptember: average high 72 °F, low 49 °F 72°49° SepOctober: average high 57 °F, low 36 °F 57°36° OctNovember: average high 40 °F, low 24 °F 40°24° NovDecember: average high 27 °F, low 11 °F 27°11° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 0.79 in precipitation 0.8 JanFebruary: 0.86 in precipitation 0.9 FebMarch: 1.72 in precipitation 1.7 MarApril: 2.64 in precipitation 2.6 AprMay: 3.79 in precipitation 3.8 MayJune: 4.21 in precipitation 4.2 JunJuly: 4.08 in precipitation 4.1 JulAugust: 4.31 in precipitation 4.3 AugSeptember: 3.38 in precipitation 3.4 SepOctober: 2.55 in precipitation 2.5 OctNovember: 1.58 in precipitation 1.6 NovDecember: 1.07 in precipitation 1.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Santiago 3 E, MN (10 mi away); precipitation: Big Lake 5.6 Nne, MN (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

553714b
Princeton, MN · 8 mi
553304b
Elk River, MN · 9 mi
553094b
Big Lake, MN · 9 mi
553774b
Santiago, MN · 12 mi
553084b
Becker, MN · 12 mi
553034b
Anoka, MN · 14 mi
550704b
Saint Francis, MN · 14 mi
550404b
Isanti, MN · 15 mi

Minnesota planting zones →

Questions about 55398

What planting zone is ZIP code 55398?

ZIP code 55398 (Zimmerman, MN) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Zimmerman, MN?

The median last spring frost (32 °F) near 55398 is May 7; after May 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Santiago 3 E station.

When is the first frost in Zimmerman, MN?

The median first fall frost near 55398 is September 28, giving a median frost-free growing season of 144 days.

When should I plant tomatoes in 55398?

Start tomato seeds indoors around Mar 12 – Mar 26 and set transplants outside around May 14 – May 28, one to three weeks after the median last frost.

How much rain and snow does 55398 get?

About 31 inches of precipitation a year (NOAA 1991–2020 normals, Big Lake 5.6 Nne station).

How hot do summers get in Zimmerman, MN?

The average high peaks at 81 °F in July, with about 7 days a year at 90 °F or more.

What kind of soil does 55398 have?

The USDA soil survey maps Isanti at the center of ZIP 55398: loamy fine sand, poorly drained, pH about 6.2 (slightly acidic).

Did spring come early in Zimmerman, MN in 2026?

Spring leaf-out near 55398 came on Apr 15 in 2026, 4 days earlier than the 1991–2020 average (Apr 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Zimmerman, MN?

Long-day onions: the longest day near 55398 is 15 h 41 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 55398 change?

Yes. The 2012 USDA map put 55398 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.