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

Planting zone for 98923 — Cowiche, WA

ZIP code 98923 (Cowiche, Yakima County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 8 and the first fall frost October 23.

Where ZIP 98923 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 8

First frostOct 23

2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cowiche, WA…

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 Cowiche, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 8median — 50% chance of a later frost

Safe for tender plantsApril 28only 10% chance of frost after

First fall frostOctober 23median — 10% chance by Oct 9

Growing season196 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 16 and returns around November 3.

From the NOAA station Yakima #2, WA — 9 miles away, elevation 1,142 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 98923

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 25 – Mar 11

SpinachSow outdoors · Feb 25 – Mar 18

Broccoli, cabbageStart indoors · Jan 28 – Feb 11

Broccoli, cabbageTransplant · Mar 18 – Apr 1

Onion setsPlant outdoors · Mar 11 – Mar 25

PotatoesPlant outdoors · Mar 18 – Apr 1

LettuceSow outdoors · Mar 11 – Mar 25

Carrots, beetsSow outdoors · Mar 18 – Apr 1

TomatoesStart indoors · Feb 11 – Feb 25

TomatoesTransplant · Apr 15 – Apr 29

Peppers, eggplantStart indoors · Jan 28 – Feb 11

Peppers, eggplantTransplant · Apr 22 – May 6

BeansSow outdoors · Apr 15 – Apr 29

Sweet cornSow outdoors · Apr 15 – Apr 29

Cucumbers, squashSow outdoors · Apr 15 – Apr 29

Fall lettuce, spinachSow outdoors · Aug 28 – Sep 11

GarlicPlant cloves · Oct 9 – Nov 13

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Oct 23) 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 98923 came on Mar 22 — 10 days earlier than the 1991–2020 average (Apr 1).

average
Apr 12026
Mar 22

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 Washington

590 plants native to the lower 48 states, recorded in Washington, 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 Cowiche, WA.

Soil in Cowiche, WA

The soil mapped at the center of ZIP 98923 is Harwood — loam, well drained.

TextureLoama good balance for most vegetables

pH7.2neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Harwood loam, 2 to 5 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 98923; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cowiche, WA

Summer high88 °Faverage high, July

Winter low26 °Faverage low, December

Hot days38days a year at 90 °F or more

Freezing nights109nights a year at 32 °F or less

Growing degree days3,038base 50 °F — the season’s usable heat

Longest day15 h 51 mindaylight on June 21

Shortest day8 h 33 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation9.8 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Yakima #2, WA (9 mi away); precipitation: Fruitvale 6.9 W, WA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

Washington planting zones →

Questions about 98923

What planting zone is ZIP code 98923?

ZIP code 98923 (Cowiche, WA) 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 Cowiche, WA?

The median last spring frost (32 °F) near 98923 is April 8; after April 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Yakima #2 station.

When is the first frost in Cowiche, WA?

The median first fall frost near 98923 is October 23, giving a median frost-free growing season of 196 days.

When should I plant tomatoes in 98923?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 98923 get?

About 9.8 inches of precipitation a year (NOAA 1991–2020 normals, Fruitvale 6.9 W station).

How hot do summers get in Cowiche, WA?

The average high peaks at 88 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 98923 have?

The USDA soil survey maps Harwood at the center of ZIP 98923: loam, well drained, pH about 7.2 (neutral).

Did spring come early in Cowiche, WA in 2026?

Spring leaf-out near 98923 came on Mar 22 in 2026, 10 days earlier than the 1991–2020 average (Apr 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cowiche, WA?

Long-day onions: the longest day near 98923 is 15 h 51 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 98923 change?

Yes. The 2012 USDA map put 98923 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.