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

Planting zone for 68023 — Fort Calhoun, NE

ZIP code 68023 (Fort Calhoun, Washington County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 19 and the first fall frost October 17.

Where ZIP 68023 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 19
First frostOct 17
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 Fort Calhoun, NE…

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 Fort Calhoun, NE

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 19median — 50% chance of a later frost
Safe for tender plantsMay 6only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 1
Growing season180 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 9 and returns around October 27.

From the NOAA station Ft Calhoun 4w, NE — 4 miles away, elevation 1,309 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 68023

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 8 – Mar 22
SpinachSow outdoors · Mar 8 – Mar 29
Broccoli, cabbageStart indoors · Feb 8 – Feb 22
Broccoli, cabbageTransplant · Mar 29 – Apr 12
Onion setsPlant outdoors · Mar 22 – Apr 5
PotatoesPlant outdoors · Mar 29 – Apr 12
LettuceSow outdoors · Mar 22 – Apr 5
Carrots, beetsSow outdoors · Mar 29 – Apr 12
TomatoesStart indoors · Feb 22 – Mar 8
TomatoesTransplant · Apr 26 – May 10
Peppers, eggplantStart indoors · Feb 8 – Feb 22
Peppers, eggplantTransplant · May 3 – May 17
BeansSow outdoors · Apr 26 – May 10
Sweet cornSow outdoors · Apr 26 – May 10
Cucumbers, squashSow outdoors · Apr 26 – May 10
Fall lettuce, spinachSow outdoors · Aug 22 – Sep 5
GarlicPlant cloves · Oct 3 – Nov 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 19) and first fall frost (Oct 17) 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 68023 came on Mar 14 — 17 days earlier than the 1991–2020 average (Mar 31).

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 Nebraska

420 plants native to the lower 48 states, recorded in Nebraska, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 31

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Fbitternut hickory75 ft · blooms mid spring · high shade tolerance · to −47 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblack oak80 ft · blooms early spring · medium shade tolerance · to −30 °F

Shrubs 55

alderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °Fbig sagebrush4 ft · blooms mid summer · high shade tolerance · to −43 °F

Wildflowers & perennials 190

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °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 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °F

Grasses 130

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbasin wildrye5 ft · blooms early spring · high shade tolerance · to −43 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °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 °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 Fort Calhoun, NE.

Soil in Fort Calhoun, NE

The soil mapped at the center of ZIP 68023 is Wathena — fine sandy loam, moderately well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH7.0neutral; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Wathena fine sandy loam, 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 68023; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fort Calhoun, NE

Summer high84 °Faverage high, July
Winter low13 °Faverage low, January
Hot days18days a year at 90 °F or more
Freezing nights140nights a year at 32 °F or less
Growing degree days3,190base 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)
Precipitation33.4 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 30 °F, low 13 °F 30°13° JanFebruary: average high 35 °F, low 16 °F 35°16° FebMarch: average high 48 °F, low 27 °F 48°27° MarApril: average high 61 °F, low 39 °F 61°39° AprMay: average high 70 °F, low 50 °F 70°50° MayJune: average high 80 °F, low 61 °F 80°61° JunJuly: average high 84 °F, low 65 °F 84°65° JulAugust: average high 82 °F, low 63 °F 82°63° AugSeptember: average high 75 °F, low 54 °F 75°54° SepOctober: average high 62 °F, low 42 °F 62°42° OctNovember: average high 47 °F, low 28 °F 47°28° NovDecember: average high 34 °F, low 18 °F 34°18° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 0.78 in precipitation 0.8 JanFebruary: 0.94 in precipitation 0.9 FebMarch: 1.76 in precipitation 1.8 MarApril: 3.30 in precipitation 3.3 AprMay: 5.01 in precipitation 5.0 MayJune: 5.06 in precipitation 5.1 JunJuly: 3.92 in precipitation 3.9 JulAugust: 4.17 in precipitation 4.2 AugSeptember: 3.31 in precipitation 3.3 SepOctober: 2.41 in precipitation 2.4 OctNovember: 1.43 in precipitation 1.4 NovDecember: 1.31 in precipitation 1.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ft Calhoun 4w, NE (4 mi away); precipitation: Ft Calhoun 4w, NE (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.

681125b
Omaha, NE · 6 mi
681525b
Omaha, NE · 7 mi
681225b
Omaha, NE · 7 mi
681426a
Omaha, NE · 8 mi
515555b
Missouri Valley, IA · 8 mi
680085b
Blair, NE · 10 mi
515425b
Honey Creek, IA · 10 mi
515265b
Crescent, IA · 10 mi

Nebraska planting zones →

Questions about 68023

What planting zone is ZIP code 68023?

ZIP code 68023 (Fort Calhoun, NE) 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 Fort Calhoun, NE?

The median last spring frost (32 °F) near 68023 is April 19; after May 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ft Calhoun 4w station.

When is the first frost in Fort Calhoun, NE?

The median first fall frost near 68023 is October 17, giving a median frost-free growing season of 180 days.

When should I plant tomatoes in 68023?

Start tomato seeds indoors around Feb 22 – Mar 8 and set transplants outside around Apr 26 – May 10, one to three weeks after the median last frost.

How much rain and snow does 68023 get?

About 33.4 inches of precipitation a year (NOAA 1991–2020 normals, Ft Calhoun 4w station).

How hot do summers get in Fort Calhoun, NE?

The average high peaks at 84 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 68023 have?

The USDA soil survey maps Wathena at the center of ZIP 68023: fine sandy loam, moderately well drained, pH about 7.0 (neutral).

Did spring come early in Fort Calhoun, NE in 2026?

Spring leaf-out near 68023 came on Mar 14 in 2026, 17 days earlier than the 1991–2020 average (Mar 31), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fort Calhoun, NE?

Long-day onions: the longest day near 68023 is 15 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).