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

Planting zone for 73720 — Bison, OK

ZIP code 73720 (Bison, Garfield County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 14 and the first fall frost October 30.

Where ZIP 73720 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.

Zone7a0 to 5 °F

Coldest night−17.8 to −15 °C

Last frostApr 14

First frostOct 30

2012 zone7a

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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Bison, OK…

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 Bison, OK

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 plantsApril 27only 10% chance of frost after

First fall frostOctober 30median — 10% chance by Oct 17

Growing season198 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around November 6.

From the NOAA station Hennessey 4 Ese, OK — 7 miles away, elevation 1,175 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 73720

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 · Sep 4 – Sep 18

GarlicPlant cloves · Oct 16 – Nov 20

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 14) and first fall frost (Oct 30) 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 73720 came on Feb 15 — 14 days earlier than the 1991–2020 average (Mar 1).

average
Mar 12026
Feb 15

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 7a in Oklahoma

511 plants native to the lower 48 states, recorded in Oklahoma, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. 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 Bison, OK.

Soil in Bison, OK

The soil mapped at the center of ZIP 73720 is Grainola — gravelly clay loam, well drained.

TextureGravelly clay loamholds water and nutrients; slow to drain and warm up

pH7.5slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Grainola-Masham complex, 3 to 5 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 73720; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Bison, OK

Summer high95 °Faverage high, July

Winter low24 °Faverage low, January

Hot days80days a year at 90 °F or more

Freezing nights94nights a year at 32 °F or less

Growing degree days4,778base 50 °F — the season’s usable heat

Longest day14 h 38 mindaylight on June 21

Shortest day9 h 41 mindaylight on December 21

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

Precipitation33.5 inper year, rain and melted snow

Snowfall9 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hennessey 4 Ese, OK (7 mi away); precipitation: Hennessey 4 Ese, OK (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

Oklahoma planting zones →

Questions about 73720

What planting zone is ZIP code 73720?

ZIP code 73720 (Bison, OK) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Bison, OK?

The median last spring frost (32 °F) near 73720 is April 14; after April 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hennessey 4 Ese station.

When is the first frost in Bison, OK?

The median first fall frost near 73720 is October 30, giving a median frost-free growing season of 198 days.

When should I plant tomatoes in 73720?

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 73720 get?

About 33.5 inches of precipitation a year and 9 inches of snowfall (NOAA 1991–2020 normals, Hennessey 4 Ese station).

How hot do summers get in Bison, OK?

The average high peaks at 95 °F in July, with about 80 days a year at 90 °F or more.

What kind of soil does 73720 have?

The USDA soil survey maps Grainola at the center of ZIP 73720: gravelly clay loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Bison, OK in 2026?

Spring leaf-out near 73720 came on Feb 15 in 2026, 14 days earlier than the 1991–2020 average (Mar 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Bison, OK?

Intermediate onions: the longest day near 73720 is 14 h 38 min, so day-neutral types bulb best; long-day varieties may not bulb fully.