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

Planting zone for 73666 — Sweetwater, OK

ZIP code 73666 (Sweetwater, Roger Mills County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 11 and the first fall frost October 26.

Where ZIP 73666 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.

Zone7b5 to 10 °F

Coldest night−15 to −12.2 °C

Last frostApr 11

First frostOct 26

2012 zone7a

Was 7a 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 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Sweetwater, 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 Sweetwater, OK

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 11median — 50% chance of a later frost

Safe for tender plantsApril 29only 10% chance of frost after

First fall frostOctober 26median — 10% chance by Oct 14

Growing season197 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 1 and returns around November 5.

From the NOAA station Erick, OK — 14 miles away, elevation 2,060 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 73666

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 28 – Mar 14

SpinachSow outdoors · Feb 28 – Mar 21

Broccoli, cabbageStart indoors · Jan 31 – Feb 14

Broccoli, cabbageTransplant · Mar 21 – Apr 4

Onion setsPlant outdoors · Mar 14 – Mar 28

PotatoesPlant outdoors · Mar 21 – Apr 4

LettuceSow outdoors · Mar 14 – Mar 28

Carrots, beetsSow outdoors · Mar 21 – Apr 4

TomatoesStart indoors · Feb 14 – Feb 28

TomatoesTransplant · Apr 18 – May 2

Peppers, eggplantStart indoors · Jan 31 – Feb 14

Peppers, eggplantTransplant · Apr 25 – May 9

BeansSow outdoors · Apr 18 – May 2

Sweet cornSow outdoors · Apr 18 – May 2

Cucumbers, squashSow outdoors · Apr 18 – May 2

Fall lettuce, spinachSow outdoors · Aug 31 – Sep 14

GarlicPlant cloves · Oct 12 – Nov 16

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 11) and first fall frost (Oct 26) 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 73666 came on Feb 12 — 13 days earlier than the 1991–2020 average (Feb 25).

average
Feb 252026
Feb 12

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 7b in Oklahoma

518 plants native to the lower 48 states, recorded in Oklahoma, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. 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 Sweetwater, OK.

Soil in Sweetwater, OK

The soil mapped at the center of ZIP 73666 is Woodward — loam, well drained.

TextureLoama good balance for most vegetables

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

DrainageWell drainednatural drainage class

Organic matter1.25%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classprime farmlandUSDA classification

Map unit: Woodward loam, 1 to 3 percent slopes.

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 73666; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Sweetwater, OK

Summer high95 °Faverage high, July

Winter low24 °Faverage low, January

Hot days83days a year at 90 °F or more

Freezing nights99nights a year at 32 °F or less

Growing degree days4,860base 50 °F — the season’s usable heat

Longest day14 h 33 mindaylight on June 21

Shortest day9 h 46 mindaylight on December 21

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

Precipitation23.3 inper year, rain and melted snow

Snowfall6 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Erick, OK (14 mi away); precipitation: Sweetwater, OK (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

Oklahoma planting zones →

Questions about 73666

What planting zone is ZIP code 73666?

ZIP code 73666 (Sweetwater, OK) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Sweetwater, OK?

The median last spring frost (32 °F) near 73666 is April 11; after April 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Erick station.

When is the first frost in Sweetwater, OK?

The median first fall frost near 73666 is October 26, giving a median frost-free growing season of 197 days.

When should I plant tomatoes in 73666?

Start tomato seeds indoors around Feb 14 – Feb 28 and set transplants outside around Apr 18 – May 2, one to three weeks after the median last frost.

How much rain and snow does 73666 get?

About 23.3 inches of precipitation a year and 6 inches of snowfall (NOAA 1991–2020 normals, Sweetwater station).

How hot do summers get in Sweetwater, OK?

The average high peaks at 95 °F in July, with about 83 days a year at 90 °F or more.

What kind of soil does 73666 have?

The USDA soil survey maps Woodward at the center of ZIP 73666: loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Sweetwater, OK in 2026?

Spring leaf-out near 73666 came on Feb 12 in 2026, 13 days earlier than the 1991–2020 average (Feb 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Sweetwater, OK?

Intermediate onions: the longest day near 73666 is 14 h 33 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 73666 change?

Yes. The 2012 USDA map put 73666 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.