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

Planting zone for 52327 — Riverside, IA

ZIP code 52327 (Riverside, Washington County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 29 and the first fall frost October 9.

Where ZIP 52327 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 29
First frostOct 9
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 Riverside, 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 Riverside, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 29median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 9median — 10% chance by Sep 25
Growing season162 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 18 and returns around October 20.

From the NOAA station Iowa City, IA — 10 miles away, elevation 640 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 52327

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 18 – Apr 1
SpinachSow outdoors · Mar 18 – Apr 8
Broccoli, cabbageStart indoors · Feb 18 – Mar 4
Broccoli, cabbageTransplant · Apr 8 – Apr 22
Onion setsPlant outdoors · Apr 1 – Apr 15
PotatoesPlant outdoors · Apr 8 – Apr 22
LettuceSow outdoors · Apr 1 – Apr 15
Carrots, beetsSow outdoors · Apr 8 – Apr 22
TomatoesStart indoors · Mar 4 – Mar 18
TomatoesTransplant · May 6 – May 20
Peppers, eggplantStart indoors · Feb 18 – Mar 4
Peppers, eggplantTransplant · May 13 – May 27
BeansSow outdoors · May 6 – May 20
Sweet cornSow outdoors · May 6 – May 20
Cucumbers, squashSow outdoors · May 6 – May 20
Fall lettuce, spinachSow outdoors · Aug 14 – Aug 28
GarlicPlant cloves · Sep 25 – Oct 30
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 29) and first fall frost (Oct 9) 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 52327 came on Mar 20 — 15 days earlier than the 1991–2020 average (Apr 4).

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 Riverside, IA.

Soil in Riverside, IA

The soil mapped at the center of ZIP 52327 is Colo — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter5%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Colo silty clay loam, 0 to 2 percent slopes, ponded, occasionally flooded.

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 52327; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Riverside, IA

Summer high84 °Faverage high, July
Winter low12 °Faverage low, January
Hot days24days a year at 90 °F or more
Freezing nights130nights a year at 32 °F or less
Growing degree days3,049base 50 °F — the season’s usable heat
Longest day15 h 11 mindaylight on June 21
Shortest day9 h 10 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation38.5 inper year, rain and melted snow
Snowfall28 inper year; 48 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 29 °F, low 12 °F 29°12° JanFebruary: average high 34 °F, low 16 °F 34°16° FebMarch: average high 48 °F, low 27 °F 48°27° MarApril: average high 62 °F, low 37 °F 62°37° AprMay: average high 72 °F, low 49 °F 72°49° MayJune: average high 81 °F, low 59 °F 81°59° JunJuly: average high 84 °F, low 63 °F 84°63° JulAugust: average high 82 °F, low 60 °F 82°60° AugSeptember: average high 76 °F, low 52 °F 76°52° SepOctober: average high 63 °F, low 40 °F 63°40° OctNovember: average high 48 °F, low 28 °F 48°28° NovDecember: average high 34 °F, low 18 °F 34°18° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 1.14 in precipitation, 7.6 in snowfall 1.1❄8 JanFebruary: 1.40 in precipitation, 7.5 in snowfall 1.4❄8 FebMarch: 2.33 in precipitation, 3.2 in snowfall 2.3❄3 MarApril: 3.86 in precipitation, 0.5 in snowfall 3.9❄1 AprMay: 5.05 in precipitation 5.0 MayJune: 5.49 in precipitation 5.5 JunJuly: 4.56 in precipitation 4.6 JulAugust: 4.32 in precipitation 4.3 AugSeptember: 3.45 in precipitation 3.5 SepOctober: 3.00 in precipitation, 0.4 in snowfall 3.0 OctNovember: 2.27 in precipitation, 1.1 in snowfall 2.3❄1 NovDecember: 1.60 in precipitation, 7.2 in snowfall 1.6❄7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Iowa City, IA (10 mi away); precipitation: Iowa City, IA (10 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

522355b
Hills, IA · 7 mi
527555b
Lone Tree, IA · 8 mi
522445b
Iowa City, IA · 8 mi
522475b
Kalona, IA · 8 mi
522015b
Ainsworth, IA · 10 mi
522405b
Iowa City, IA · 11 mi
522465b
Iowa City, IA · 12 mi
522425b
Iowa City, IA · 13 mi

Iowa planting zones →

Questions about 52327

What planting zone is ZIP code 52327?

ZIP code 52327 (Riverside, 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 Riverside, IA?

The median last spring frost (32 °F) near 52327 is April 29; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Iowa City station.

When is the first frost in Riverside, IA?

The median first fall frost near 52327 is October 9, giving a median frost-free growing season of 162 days.

When should I plant tomatoes in 52327?

Start tomato seeds indoors around Mar 4 – Mar 18 and set transplants outside around May 6 – May 20, one to three weeks after the median last frost.

How much rain and snow does 52327 get?

About 38.5 inches of precipitation a year and 28 inches of snowfall (NOAA 1991–2020 normals, Iowa City station).

How hot do summers get in Riverside, IA?

The average high peaks at 84 °F in July, with about 24 days a year at 90 °F or more.

What kind of soil does 52327 have?

The USDA soil survey maps Colo at the center of ZIP 52327: silty clay loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Riverside, IA in 2026?

Spring leaf-out near 52327 came on Mar 20 in 2026, 15 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Riverside, IA?

Long-day onions: the longest day near 52327 is 15 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).