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

Planting zone for 99337 — Kennewick, WA

ZIP code 99337 (Kennewick, Benton County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is March 28 and the first fall frost October 30.

Where ZIP 99337 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 frostMar 28
First frostOct 30
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 Kennewick, 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 Kennewick, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 28median — 50% chance of a later frost
Safe for tender plantsApril 10only 10% chance of frost after
First fall frostOctober 30median — 10% chance by Oct 18
Growing season216 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 8 and returns around November 11.

From the NOAA station Kennewick, WA — 11 miles away, elevation 390 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 99337

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 14 – Feb 28
SpinachSow outdoors · Feb 14 – Mar 7
Broccoli, cabbageStart indoors · Jan 17 – Jan 31
Broccoli, cabbageTransplant · Mar 7 – Mar 21
Onion setsPlant outdoors · Feb 28 – Mar 14
PotatoesPlant outdoors · Mar 7 – Mar 21
LettuceSow outdoors · Feb 28 – Mar 14
Carrots, beetsSow outdoors · Mar 7 – Mar 21
TomatoesStart indoors · Jan 31 – Feb 14
TomatoesTransplant · Apr 4 – Apr 18
Peppers, eggplantStart indoors · Jan 17 – Jan 31
Peppers, eggplantTransplant · Apr 11 – Apr 25
BeansSow outdoors · Apr 4 – Apr 18
Sweet cornSow outdoors · Apr 4 – Apr 18
Cucumbers, squashSow outdoors · Apr 4 – Apr 18
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 (Mar 28) 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 99337 came on Mar 5 — 11 days earlier than the 1991–2020 average (Mar 16).

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 Washington

592 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

Trees 31

Alaska cedar75 ft · blooms mid spring · low shade tolerance · to −22 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fbigleaf maple60 ft · blooms mid spring · medium shade tolerance · to −14 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °F

Shrubs 105

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FBarclay's willow15 ft · high shade tolerance · to −43 °F

Wildflowers & perennials 284

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 157

Alaska brome5 ft · blooms late spring · low shade tolerance · to −18 °FAlaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °F

Vines 3

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

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 Kennewick, WA.

Soil in Kennewick, WA

The soil mapped at the center of ZIP 99337 is Ritzville — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH7.5slightly alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Ritzville silt loam, 0 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 99337; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kennewick, WA

Summer high91 °Faverage high, July
Winter low29 °Faverage low, January
Hot days48days a year at 90 °F or more
Freezing nights76nights a year at 32 °F or less
Growing degree days3,502base 50 °F — the season’s usable heat
Longest day15 h 46 mindaylight on June 21
Shortest day8 h 38 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation7.9 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 42 °F, low 29 °F 42°29° JanFebruary: average high 48 °F, low 31 °F 48°31° FebMarch: average high 58 °F, low 36 °F 58°36° MarApril: average high 66 °F, low 42 °F 66°42° AprMay: average high 75 °F, low 50 °F 75°50° MayJune: average high 82 °F, low 56 °F 82°56° JunJuly: average high 91 °F, low 62 °F 91°62° JulAugust: average high 90 °F, low 61 °F 90°61° AugSeptember: average high 81 °F, low 53 °F 81°53° SepOctober: average high 66 °F, low 43 °F 66°43° OctNovember: average high 51 °F, low 35 °F 51°35° NovDecember: average high 42 °F, low 30 °F 42°30° Dec

Precipitation by month inches

0″1″2″January: 1.13 in precipitation 1.1 JanFebruary: 0.79 in precipitation 0.8 FebMarch: 0.66 in precipitation 0.7 MarApril: 0.61 in precipitation 0.6 AprMay: 0.84 in precipitation 0.8 MayJune: 0.58 in precipitation 0.6 JunJuly: 0.21 in precipitation 0.2 JulAugust: 0.17 in precipitation 0.2 AugSeptember: 0.26 in precipitation 0.3 SepOctober: 0.67 in precipitation 0.7 OctNovember: 0.87 in precipitation 0.9 NovDecember: 1.08 in precipitation 1.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Kennewick, WA (11 mi away); precipitation: Kennewick, WA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

993467b
Plymouth, WA · 10 mi
993637b
Wallula, WA · 10 mi
993367b
Kennewick, WA · 12 mi
993387b
Kennewick, WA · 12 mi
993027b
Pasco, WA · 13 mi
993237a
Burbank, WA · 14 mi
978827b
Umatilla, OR · 16 mi
993527b
Richland, WA · 16 mi

All 3 ZIP codes in Kennewick → · Washington planting zones →

Questions about 99337

What planting zone is ZIP code 99337?

ZIP code 99337 (Kennewick, 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 Kennewick, WA?

The median last spring frost (32 °F) near 99337 is March 28; after April 10 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kennewick station.

When is the first frost in Kennewick, WA?

The median first fall frost near 99337 is October 30, giving a median frost-free growing season of 216 days.

When should I plant tomatoes in 99337?

Start tomato seeds indoors around Jan 31 – Feb 14 and set transplants outside around Apr 4 – Apr 18, one to three weeks after the median last frost.

How much rain and snow does 99337 get?

About 7.9 inches of precipitation a year (NOAA 1991–2020 normals, Kennewick station).

How hot do summers get in Kennewick, WA?

The average high peaks at 91 °F in July, with about 48 days a year at 90 °F or more.

What kind of soil does 99337 have?

The USDA soil survey maps Ritzville at the center of ZIP 99337: silt loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Kennewick, WA in 2026?

Spring leaf-out near 99337 came on Mar 5 in 2026, 11 days earlier than the 1991–2020 average (Mar 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Kennewick, WA?

Long-day onions: the longest day near 99337 is 15 h 46 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99337 change?

Yes. The 2012 USDA map put 99337 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.