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

Planting zone for 99359 — Starbuck, WA

ZIP code 99359 (Starbuck, Columbia County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 28 and the first fall frost October 13.

Where ZIP 99359 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 28

First frostOct 13

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 Starbuck, 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 Starbuck, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 28median — 50% chance of a later frost

Safe for tender plantsMay 14only 10% chance of frost after

First fall frostOctober 13median — 10% chance by Sep 30

Growing season168 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 6 and returns around October 25.

From the NOAA station Dayton 1 Wsw, WA — 16 miles away, elevation 1,558 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 99359

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 17 – Mar 31

SpinachSow outdoors · Mar 17 – Apr 7

Broccoli, cabbageStart indoors · Feb 17 – Mar 3

Broccoli, cabbageTransplant · Apr 7 – Apr 21

Onion setsPlant outdoors · Mar 31 – Apr 14

PotatoesPlant outdoors · Apr 7 – Apr 21

LettuceSow outdoors · Mar 31 – Apr 14

Carrots, beetsSow outdoors · Apr 7 – Apr 21

TomatoesStart indoors · Mar 3 – Mar 17

TomatoesTransplant · May 5 – May 19

Peppers, eggplantStart indoors · Feb 17 – Mar 3

Peppers, eggplantTransplant · May 12 – May 26

BeansSow outdoors · May 5 – May 19

Sweet cornSow outdoors · May 5 – May 19

Cucumbers, squashSow outdoors · May 5 – May 19

Fall lettuce, spinachSow outdoors · Aug 18 – Sep 1

GarlicPlant cloves · Sep 29 – Nov 3

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 13) 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 99359 came on Mar 2 — 9 days earlier than the 1991–2020 average (Mar 11).

average
Mar 112026
Mar 2

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 Starbuck, WA

The soil mapped at the center of ZIP 99359 is Kuhl — gravelly silt loam, well drained.

TextureGravelly silt loama good balance for most vegetables

pH7.6slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Kuhl extremely rocky silt loam, 30 to 65 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 99359; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Starbuck, WA

Summer high88 °Faverage high, July

Winter low26 °Faverage low, January

Hot days31days a year at 90 °F or more

Freezing nights113nights a year at 32 °F or less

Growing degree days2,541base 50 °F — the season’s usable heat

Longest day15 h 50 mindaylight on June 21

Shortest day8 h 34 mindaylight on December 21

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

Precipitation18.8 inper year, rain and melted snow

Snowfall16 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Dayton 1 Wsw, WA (16 mi away); precipitation: Dayton 1 Wsw, WA (16 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Waitsburg, WA · 19 mi

993717a

Washtucna, WA · 20 mi

Washington planting zones →

Questions about 99359

What planting zone is ZIP code 99359?

ZIP code 99359 (Starbuck, WA) 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 Starbuck, WA?

The median last spring frost (32 °F) near 99359 is April 28; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dayton 1 Wsw station.

When is the first frost in Starbuck, WA?

The median first fall frost near 99359 is October 13, giving a median frost-free growing season of 168 days.

When should I plant tomatoes in 99359?

Start tomato seeds indoors around Mar 3 – Mar 17 and set transplants outside around May 5 – May 19, one to three weeks after the median last frost.

How much rain and snow does 99359 get?

About 18.8 inches of precipitation a year and 16 inches of snowfall (NOAA 1991–2020 normals, Dayton 1 Wsw station).

How hot do summers get in Starbuck, WA?

The average high peaks at 88 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 99359 have?

The USDA soil survey maps Kuhl at the center of ZIP 99359: gravelly silt loam, well drained, pH about 7.6 (slightly alkaline).

Did spring come early in Starbuck, WA in 2026?

Spring leaf-out near 99359 came on Mar 2 in 2026, 9 days earlier than the 1991–2020 average (Mar 11), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Starbuck, WA?

Long-day onions: the longest day near 99359 is 15 h 50 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99359 change?

Yes. The 2012 USDA map put 99359 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.