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

Planting zone for 68629 — Clarkson, NE

ZIP code 68629 (Clarkson, Colfax County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 27 and the first fall frost October 10.

Where ZIP 68629 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 27
First frostOct 10
2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Clarkson, 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 Clarkson, NE

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 27median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 10median — 10% chance by Sep 28
Growing season165 daysfrost-free, median

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

From the NOAA station Clarkson, NE — within 1 mile, elevation 1,549 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 68629

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 16 – Mar 30
SpinachSow outdoors · Mar 16 – Apr 6
Broccoli, cabbageStart indoors · Feb 16 – Mar 2
Broccoli, cabbageTransplant · Apr 6 – Apr 20
Onion setsPlant outdoors · Mar 30 – Apr 13
PotatoesPlant outdoors · Apr 6 – Apr 20
LettuceSow outdoors · Mar 30 – Apr 13
Carrots, beetsSow outdoors · Apr 6 – Apr 20
TomatoesStart indoors · Mar 2 – Mar 16
TomatoesTransplant · May 4 – May 18
Peppers, eggplantStart indoors · Feb 16 – Mar 2
Peppers, eggplantTransplant · May 11 – May 25
BeansSow outdoors · May 4 – May 18
Sweet cornSow outdoors · May 4 – May 18
Cucumbers, squashSow outdoors · May 4 – May 18
Fall lettuce, spinachSow outdoors · Aug 15 – Aug 29
GarlicPlant cloves · Sep 26 – Oct 31
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 10) 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 68629 came on Mar 18 — 18 days earlier than the 1991–2020 average (Apr 5).

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).

Soil in Clarkson, NE

The soil mapped at the center of ZIP 68629 is Nora — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.8neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Nora-Crofton complex, 11 to 17 percent slopes, eroded.

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 68629; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Clarkson, NE

Summer high86 °Faverage high, July
Winter low11 °Faverage low, January
Hot days26days a year at 90 °F or more
Freezing nights156nights a year at 32 °F or less
Growing degree days3,101base 50 °F — the season’s usable heat
Longest day15 h 12 mindaylight on June 21
Shortest day9 h 09 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation28.1 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 31 °F, low 11 °F 31°11° JanFebruary: average high 36 °F, low 15 °F 36°15° FebMarch: average high 49 °F, low 25 °F 49°25° MarApril: average high 61 °F, low 37 °F 61°37° AprMay: average high 72 °F, low 48 °F 72°48° MayJune: average high 82 °F, low 60 °F 82°60° JunJuly: average high 86 °F, low 64 °F 86°64° JulAugust: average high 83 °F, low 62 °F 83°62° AugSeptember: average high 76 °F, low 52 °F 76°52° SepOctober: average high 63 °F, low 38 °F 63°38° OctNovember: average high 47 °F, low 25 °F 47°25° NovDecember: average high 35 °F, low 16 °F 35°16° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 0.26 in precipitation 0.3 JanFebruary: 0.42 in precipitation 0.4 FebMarch: 1.38 in precipitation 1.4 MarApril: 3.09 in precipitation 3.1 AprMay: 4.41 in precipitation 4.4 MayJune: 4.82 in precipitation 4.8 JunJuly: 3.17 in precipitation 3.2 JulAugust: 3.74 in precipitation 3.7 AugSeptember: 2.82 in precipitation 2.8 SepOctober: 2.30 in precipitation 2.3 OctNovember: 1.23 in precipitation 1.2 NovDecember: 0.47 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Clarkson, NE (within 1 mile); precipitation: Clarkson 3.1 Ese, NE (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

686415b
Howells, NE · 6 mi
686435b
Leigh, NE · 7 mi
686315b
Creston, NE · 12 mi
686335b
Dodge, NE · 12 mi
686615b
Schuyler, NE · 15 mi
686595b
Rogers, NE · 15 mi
687795b
Stanton, NE · 17 mi
686645b
Snyder, NE · 18 mi

Nebraska planting zones →

Questions about 68629

What planting zone is ZIP code 68629?

ZIP code 68629 (Clarkson, 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 Clarkson, NE?

The median last spring frost (32 °F) near 68629 is April 27; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Clarkson station.

When is the first frost in Clarkson, NE?

The median first fall frost near 68629 is October 10, giving a median frost-free growing season of 165 days.

When should I plant tomatoes in 68629?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 68629 get?

About 28.1 inches of precipitation a year (NOAA 1991–2020 normals, Clarkson 3.1 Ese station).

How hot do summers get in Clarkson, NE?

The average high peaks at 86 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 68629 have?

The USDA soil survey maps Nora at the center of ZIP 68629: silt loam, well drained, pH about 6.8 (neutral).

Did spring come early in Clarkson, NE in 2026?

Spring leaf-out near 68629 came on Mar 18 in 2026, 18 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Clarkson, NE?

Long-day onions: the longest day near 68629 is 15 h 12 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 68629 change?

Yes. The 2012 USDA map put 68629 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.