Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 66419 — Denison, KS

ZIP code 66419 (Denison, Jackson County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 10 and the first fall frost October 29.

Where ZIP 66419 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 10

First frostOct 29

2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Denison, KS…

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 Denison, KS

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 10median — 50% chance of a later frost

Safe for tender plantsApril 25only 10% chance of frost after

First fall frostOctober 29median — 10% chance by Oct 12

Growing season199 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 1 and returns around November 6.

From the NOAA station Valley Falls 3 Sw, KS — 7 miles away, elevation 1,050 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 66419

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 27 – Mar 13

SpinachSow outdoors · Feb 27 – Mar 20

Broccoli, cabbageStart indoors · Jan 30 – Feb 13

Broccoli, cabbageTransplant · Mar 20 – Apr 3

Onion setsPlant outdoors · Mar 13 – Mar 27

PotatoesPlant outdoors · Mar 20 – Apr 3

LettuceSow outdoors · Mar 13 – Mar 27

Carrots, beetsSow outdoors · Mar 20 – Apr 3

TomatoesStart indoors · Feb 13 – Feb 27

TomatoesTransplant · Apr 17 – May 1

Peppers, eggplantStart indoors · Jan 30 – Feb 13

Peppers, eggplantTransplant · Apr 24 – May 8

BeansSow outdoors · Apr 17 – May 1

Sweet cornSow outdoors · Apr 17 – May 1

Cucumbers, squashSow outdoors · Apr 17 – May 1

Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17

GarlicPlant cloves · Oct 15 – Nov 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Oct 29) 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 66419 came on Feb 28 — 19 days earlier than the 1991–2020 average (Mar 19).

average
Mar 192026
Feb 28

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 Kansas

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

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 Denison, KS.

Soil in Denison, KS

The soil mapped at the center of ZIP 66419 is Pawnee — clay loam, moderately well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH5.6moderately acidic; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter2%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Pawnee clay loam, 4 to 8 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 66419; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Denison, KS

Summer high91 °Faverage high, July

Winter low18 °Faverage low, January

Hot days57days a year at 90 °F or more

Freezing nights118nights a year at 32 °F or less

Growing degree days4,106base 50 °F — the season’s usable heat

Longest day14 h 57 mindaylight on June 21

Shortest day9 h 23 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation37.6 inper year, rain and melted snow

Snowfall14 inper year; 15 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Valley Falls 3 Sw, KS (7 mi away); precipitation: Valley Falls 3 Sw, KS (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

664406b

Hoyt, KS · 8 mi

660886b

Valley Falls, KS · 8 mi

Nortonville, KS · 15 mi

Kansas planting zones →

Questions about 66419

What planting zone is ZIP code 66419?

ZIP code 66419 (Denison, KS) 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 Denison, KS?

The median last spring frost (32 °F) near 66419 is April 10; after April 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Valley Falls 3 Sw station.

When is the first frost in Denison, KS?

The median first fall frost near 66419 is October 29, giving a median frost-free growing season of 199 days.

When should I plant tomatoes in 66419?

Start tomato seeds indoors around Feb 13 – Feb 27 and set transplants outside around Apr 17 – May 1, one to three weeks after the median last frost.

How much rain and snow does 66419 get?

About 37.6 inches of precipitation a year and 14 inches of snowfall (NOAA 1991–2020 normals, Valley Falls 3 Sw station).

How hot do summers get in Denison, KS?

The average high peaks at 91 °F in July, with about 57 days a year at 90 °F or more.

What kind of soil does 66419 have?

The USDA soil survey maps Pawnee at the center of ZIP 66419: clay loam, moderately well drained, pH about 5.6 (moderately acidic).

Did spring come early in Denison, KS in 2026?

Spring leaf-out near 66419 came on Feb 28 in 2026, 19 days earlier than the 1991–2020 average (Mar 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Denison, KS?

Intermediate onions: the longest day near 66419 is 14 h 57 min, so day-neutral types bulb best; long-day varieties may not bulb fully.