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

Planting zone for 52646 — Oakville, IA

ZIP code 52646 (Oakville, Louisa County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 14 and the first fall frost October 24.

Where ZIP 52646 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostApr 14
First frostOct 24
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Oakville, 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 Oakville, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 14median — 50% chance of a later frost
Safe for tender plantsMay 2only 10% chance of frost after
First fall frostOctober 24median — 10% chance by Oct 9
Growing season190 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 5 and returns around November 1.

From the NOAA station New Boston Dam 17, IL — 9 miles away, elevation 548 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 52646

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 3 – Mar 17
SpinachSow outdoors · Mar 3 – Mar 24
Broccoli, cabbageStart indoors · Feb 3 – Feb 17
Broccoli, cabbageTransplant · Mar 24 – Apr 7
Onion setsPlant outdoors · Mar 17 – Mar 31
PotatoesPlant outdoors · Mar 24 – Apr 7
LettuceSow outdoors · Mar 17 – Mar 31
Carrots, beetsSow outdoors · Mar 24 – Apr 7
TomatoesStart indoors · Feb 17 – Mar 3
TomatoesTransplant · Apr 21 – May 5
Peppers, eggplantStart indoors · Feb 3 – Feb 17
Peppers, eggplantTransplant · Apr 28 – May 12
BeansSow outdoors · Apr 21 – May 5
Sweet cornSow outdoors · Apr 21 – May 5
Cucumbers, squashSow outdoors · Apr 21 – May 5
Fall lettuce, spinachSow outdoors · Aug 29 – Sep 12
GarlicPlant cloves · Oct 10 – Nov 14
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 14) and first fall frost (Oct 24) 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 52646 came on Mar 15 — 17 days earlier than the 1991–2020 average (Apr 1).

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 5b in Iowa

473 plants native to the lower 48 states, recorded in Iowa, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. 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 77

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 191

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 136

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 7

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 honeysuckle16 ft · blooms late summer · low 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 Oakville, IA.

Soil in Oakville, IA

The soil mapped at the center of ZIP 52646 is Shaffton — loam, somewhat poorly drained.

TextureLoama good balance for most vegetables
pH6.2slightly acidic; 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 farmlandUSDA classification

Map unit: Shaffton loam, 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 52646; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Oakville, IA

Summer high86 °Faverage high, July
Winter low15 °Faverage low, January
Hot days24days a year at 90 °F or more
Freezing nights122nights a year at 32 °F or less
Growing degree days3,439base 50 °F — the season’s usable heat
Longest day15 h 08 mindaylight on June 21
Shortest day9 h 13 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation37.3 inper year, rain and melted snow
Snowfall20 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 15 °F 32°15° JanFebruary: average high 36 °F, low 19 °F 36°19° FebMarch: average high 49 °F, low 30 °F 49°30° MarApril: average high 62 °F, low 40 °F 62°40° AprMay: average high 73 °F, low 52 °F 73°52° MayJune: average high 83 °F, low 62 °F 83°62° JunJuly: average high 86 °F, low 65 °F 86°65° JulAugust: average high 84 °F, low 63 °F 84°63° AugSeptember: average high 77 °F, low 55 °F 77°55° SepOctober: average high 64 °F, low 43 °F 64°43° OctNovember: average high 49 °F, low 32 °F 49°32° NovDecember: average high 37 °F, low 22 °F 37°22° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 1.55 in precipitation, 6.8 in snowfall 1.6❄7 JanFebruary: 1.91 in precipitation, 3.9 in snowfall 1.9❄4 FebMarch: 2.43 in precipitation, 3.4 in snowfall 2.4❄3 MarApril: 3.83 in precipitation, 0.6 in snowfall 3.8❄1 AprMay: 4.82 in precipitation 4.8 MayJune: 4.80 in precipitation 4.8 JunJuly: 3.49 in precipitation 3.5 JulAugust: 3.53 in precipitation 3.5 AugSeptember: 3.83 in precipitation 3.8 SepOctober: 2.80 in precipitation 2.8 OctNovember: 2.24 in precipitation, 0.5 in snowfall 2.2❄1 NovDecember: 2.04 in precipitation, 5.2 in snowfall 2.0❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: New Boston Dam 17, IL (9 mi away); precipitation: Keithsburg, IL (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.

614425b
Keithsburg, IL · 5 mi
526375b
Mediapolis, IA · 8 mi
526535b
Wapello, IA · 10 mi
614695b
Oquawka, IL · 10 mi
614765b
Seaton, IL · 10 mi
526506a
Sperry, IA · 11 mi
612725b
New Boston, IL · 13 mi
612605b
Joy, IL · 13 mi

Iowa planting zones →

Questions about 52646

What planting zone is ZIP code 52646?

ZIP code 52646 (Oakville, IA) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Oakville, IA?

The median last spring frost (32 °F) near 52646 is April 14; after May 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, New Boston Dam 17 station.

When is the first frost in Oakville, IA?

The median first fall frost near 52646 is October 24, giving a median frost-free growing season of 190 days.

When should I plant tomatoes in 52646?

Start tomato seeds indoors around Feb 17 – Mar 3 and set transplants outside around Apr 21 – May 5, one to three weeks after the median last frost.

How much rain and snow does 52646 get?

About 37.3 inches of precipitation a year and 20 inches of snowfall (NOAA 1991–2020 normals, Keithsburg station).

How hot do summers get in Oakville, IA?

The average high peaks at 86 °F in July, with about 24 days a year at 90 °F or more.

What kind of soil does 52646 have?

The USDA soil survey maps Shaffton at the center of ZIP 52646: loam, somewhat poorly drained, pH about 6.2 (slightly acidic).

Did spring come early in Oakville, IA in 2026?

Spring leaf-out near 52646 came on Mar 15 in 2026, 17 days earlier than the 1991–2020 average (Apr 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Oakville, IA?

Long-day onions: the longest day near 52646 is 15 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).