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

Planting zone for 99324 — College Place, WA

ZIP code 99324 (College Place, Walla Walla County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is May 2 and the first fall frost October 1.

Where ZIP 99324 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 frostMay 2
First frostOct 1
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 College Place, 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 College Place, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 2median — 50% chance of a later frost
Safe for tender plantsMay 18only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 14
Growing season151 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 15 and returns around October 12.

From the NOAA station Whitman Mission, WA — 4 miles away, elevation 633 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 99324

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 21 – Apr 4
SpinachSow outdoors · Mar 21 – Apr 11
Broccoli, cabbageStart indoors · Feb 21 – Mar 7
Broccoli, cabbageTransplant · Apr 11 – Apr 25
Onion setsPlant outdoors · Apr 4 – Apr 18
PotatoesPlant outdoors · Apr 11 – Apr 25
LettuceSow outdoors · Apr 4 – Apr 18
Carrots, beetsSow outdoors · Apr 11 – Apr 25
TomatoesStart indoors · Mar 7 – Mar 21
TomatoesTransplant · May 9 – May 23
Peppers, eggplantStart indoors · Feb 21 – Mar 7
Peppers, eggplantTransplant · May 16 – May 30
BeansSow outdoors · May 9 – May 23
Sweet cornSow outdoors · May 9 – May 23
Cucumbers, squashSow outdoors · May 9 – May 23
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 2) and first fall frost (Oct 1) 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 99324 came on Mar 1 — 4 days earlier than the 1991–2020 average (Mar 5).

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.

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 282

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 College Place, WA.

Soil in College Place, WA

The soil mapped at the center of ZIP 99324 is Touchet — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH7.6slightly alkaline; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2%moderate
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Touchet silt loam, 0 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 99324; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in College Place, WA

Summer high90 °Faverage high, July
Winter low27 °Faverage low, January
Hot days44days a year at 90 °F or more
Freezing nights125nights a year at 32 °F or less
Growing degree days2,616base 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)
Precipitation15.4 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 27 °F 42°27° JanFebruary: average high 48 °F, low 28 °F 48°28° FebMarch: average high 57 °F, low 32 °F 57°32° MarApril: average high 65 °F, low 37 °F 65°37° AprMay: average high 73 °F, low 44 °F 73°44° MayJune: average high 80 °F, low 49 °F 80°49° JunJuly: average high 90 °F, low 54 °F 90°54° JulAugust: average high 90 °F, low 52 °F 90°52° AugSeptember: average high 80 °F, low 44 °F 80°44° SepOctober: average high 66 °F, low 36 °F 66°36° OctNovember: average high 50 °F, low 31 °F 50°31° NovDecember: average high 41 °F, low 27 °F 41°27° Dec

Precipitation by month inches

0″1″2″January: 1.68 in precipitation 1.7 JanFebruary: 1.38 in precipitation 1.4 FebMarch: 1.70 in precipitation 1.7 MarApril: 1.53 in precipitation 1.5 AprMay: 1.80 in precipitation 1.8 MayJune: 1.14 in precipitation 1.1 JunJuly: 0.38 in precipitation 0.4 JulAugust: 0.40 in precipitation 0.4 AugSeptember: 0.68 in precipitation 0.7 SepOctober: 1.30 in precipitation 1.3 OctNovember: 1.67 in precipitation 1.7 NovDecember: 1.73 in precipitation 1.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Whitman Mission, WA (4 mi away); precipitation: Whitman Mission, WA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

993627a
Walla Walla, WA · 5 mi
978627a
Milton Freewater, OR · 9 mi
993297a
Dixie, WA · 13 mi
993607a
Touchet, WA · 14 mi
978137a
Athena, OR · 15 mi
978867a
Weston, OR · 18 mi
993617a
Waitsburg, WA · 18 mi
978357a
Helix, OR · 21 mi

Washington planting zones →

Questions about 99324

What planting zone is ZIP code 99324?

ZIP code 99324 (College Place, 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 College Place, WA?

The median last spring frost (32 °F) near 99324 is May 2; after May 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Whitman Mission station.

When is the first frost in College Place, WA?

The median first fall frost near 99324 is October 1, giving a median frost-free growing season of 151 days.

When should I plant tomatoes in 99324?

Start tomato seeds indoors around Mar 7 – Mar 21 and set transplants outside around May 9 – May 23, one to three weeks after the median last frost.

How much rain and snow does 99324 get?

About 15.4 inches of precipitation a year (NOAA 1991–2020 normals, Whitman Mission station).

How hot do summers get in College Place, WA?

The average high peaks at 90 °F in July, with about 44 days a year at 90 °F or more.

What kind of soil does 99324 have?

The USDA soil survey maps Touchet at the center of ZIP 99324: silt loam, moderately well drained, pH about 7.6 (slightly alkaline).

Did spring come early in College Place, WA in 2026?

Spring leaf-out near 99324 came on Mar 1 in 2026, 4 days earlier than the 1991–2020 average (Mar 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in College Place, WA?

Long-day onions: the longest day near 99324 is 15 h 46 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).