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

Planting zone for 52620 — Bonaparte, IA

ZIP code 52620 (Bonaparte, Van Buren County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 26 and the first fall frost October 13.

Where ZIP 52620 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 frostApr 26
First frostOct 13
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Bonaparte, IA…

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 Bonaparte, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 26median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 13median — 10% chance by Sep 28
Growing season169 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 23.

From the NOAA station Keosauqua, IA — 9 miles away, elevation 630 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 52620

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 15 – Mar 29
SpinachSow outdoors · Mar 15 – Apr 5
Broccoli, cabbageStart indoors · Feb 15 – Mar 1
Broccoli, cabbageTransplant · Apr 5 – Apr 19
Onion setsPlant outdoors · Mar 29 – Apr 12
PotatoesPlant outdoors · Apr 5 – Apr 19
LettuceSow outdoors · Mar 29 – Apr 12
Carrots, beetsSow outdoors · Apr 5 – Apr 19
TomatoesStart indoors · Mar 1 – Mar 15
TomatoesTransplant · May 3 – May 17
Peppers, eggplantStart indoors · Feb 15 – Mar 1
Peppers, eggplantTransplant · May 10 – May 24
BeansSow outdoors · May 3 – May 17
Sweet cornSow outdoors · May 3 – May 17
Cucumbers, squashSow outdoors · May 3 – May 17
Fall lettuce, spinachSow outdoors · Aug 18 – Sep 1
GarlicPlant cloves · Sep 29 – Nov 3
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 13) 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 52620 came on Mar 11 — 18 days earlier than the 1991–2020 average (Mar 29).

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 Iowa

482 plants native to the lower 48 states, recorded in Iowa, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 49

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °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 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °F

Shrubs 79

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 195

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 137

arctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid 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 °Fblue grama1 ft · blooms early summer · high shade tolerance · to −43 °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 Bonaparte, IA.

Soil in Bonaparte, IA

The soil mapped at the center of ZIP 52620 is Gorin — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH5.9moderately acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter1.25%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Gorin silt loam, 9 to 14 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 52620; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Bonaparte, IA

Summer high86 °Faverage high, July
Winter low14 °Faverage low, January
Hot days32days a year at 90 °F or more
Freezing nights128nights a year at 32 °F or less
Growing degree days3,356base 50 °F — the season’s usable heat
Longest day15 h 06 mindaylight on June 21
Shortest day9 h 15 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation39.7 inper year, rain and melted snow
Snowfall23 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 32 °F, low 14 °F 32°14° JanFebruary: average high 37 °F, low 17 °F 37°17° FebMarch: average high 50 °F, low 29 °F 50°29° MarApril: average high 63 °F, low 39 °F 63°39° AprMay: average high 73 °F, low 51 °F 73°51° MayJune: average high 82 °F, low 60 °F 82°60° JunJuly: average high 86 °F, low 65 °F 86°65° JulAugust: average high 85 °F, low 62 °F 85°62° AugSeptember: average high 78 °F, low 53 °F 78°53° SepOctober: average high 65 °F, low 42 °F 65°42° OctNovember: average high 49 °F, low 29 °F 49°29° NovDecember: average high 37 °F, low 20 °F 37°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 1.50 in precipitation, 7.3 in snowfall 1.5❄7 JanFebruary: 2.11 in precipitation, 5.3 in snowfall 2.1❄5 FebMarch: 2.45 in precipitation, 2.7 in snowfall 2.5❄3 MarApril: 3.64 in precipitation, 0.9 in snowfall 3.6❄1 AprMay: 5.67 in precipitation 5.7 MayJune: 5.29 in precipitation 5.3 JunJuly: 4.48 in precipitation 4.5 JulAugust: 3.60 in precipitation 3.6 AugSeptember: 3.69 in precipitation 3.7 SepOctober: 2.97 in precipitation, 0.2 in snowfall 3.0 OctNovember: 2.35 in precipitation, 1.1 in snowfall 2.4❄1 NovDecember: 1.96 in precipitation, 5.5 in snowfall 2.0❄6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Keosauqua, IA (9 mi away); precipitation: Keosauqua, IA (9 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.

526266a
Farmington, IA · 6 mi
525655b
Keosauqua, IA · 8 mi
525736a
Mount Sterling, IA · 9 mi
526306a
Hillsboro, IA · 9 mi
526316a
Houghton, IA · 11 mi
526516a
Stockport, IA · 11 mi
526256a
Donnellson, IA · 12 mi
526496a
Salem, IA · 13 mi

Iowa planting zones →

Questions about 52620

What planting zone is ZIP code 52620?

ZIP code 52620 (Bonaparte, IA) 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 Bonaparte, IA?

The median last spring frost (32 °F) near 52620 is April 26; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Keosauqua station.

When is the first frost in Bonaparte, IA?

The median first fall frost near 52620 is October 13, giving a median frost-free growing season of 169 days.

When should I plant tomatoes in 52620?

Start tomato seeds indoors around Mar 1 – Mar 15 and set transplants outside around May 3 – May 17, one to three weeks after the median last frost.

How much rain and snow does 52620 get?

About 39.7 inches of precipitation a year and 23 inches of snowfall (NOAA 1991–2020 normals, Keosauqua station).

How hot do summers get in Bonaparte, IA?

The average high peaks at 86 °F in July, with about 32 days a year at 90 °F or more.

What kind of soil does 52620 have?

The USDA soil survey maps Gorin at the center of ZIP 52620: silt loam, somewhat poorly drained, pH about 5.9 (moderately acidic).

Did spring come early in Bonaparte, IA in 2026?

Spring leaf-out near 52620 came on Mar 11 in 2026, 18 days earlier than the 1991–2020 average (Mar 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Bonaparte, IA?

Long-day onions: the longest day near 52620 is 15 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 52620 change?

Yes. The 2012 USDA map put 52620 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.