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

Planting zone for 99018 — Latah, WA

ZIP code 99018 (Latah, Spokane County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 11 and the first fall frost October 5.

Where ZIP 99018 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.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostMay 11

First frostOct 5

2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Latah, 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 Latah, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

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

Safe for tender plantsJune 4only 10% chance of frost after

First fall frostOctober 5median — 10% chance by Sep 15

Growing season143 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 19.

From the NOAA station Plummer 3 Wsw, ID — 9 miles away, elevation 2,904 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 99018

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 30 – Apr 13

SpinachSow outdoors · Mar 30 – Apr 20

Broccoli, cabbageStart indoors · Mar 2 – Mar 16

Broccoli, cabbageTransplant · Apr 20 – May 4

Onion setsPlant outdoors · Apr 13 – Apr 27

PotatoesPlant outdoors · Apr 20 – May 4

LettuceSow outdoors · Apr 13 – Apr 27

Carrots, beetsSow outdoors · Apr 20 – May 4

TomatoesStart indoors · Mar 16 – Mar 30

TomatoesTransplant · May 18 – Jun 1

Peppers, eggplantStart indoors · Mar 2 – Mar 16

Peppers, eggplantTransplant · May 25 – Jun 8

BeansSow outdoors · May 18 – Jun 1

Sweet cornSow outdoors · May 18 – Jun 1

Cucumbers, squashSow outdoors · May 18 – Jun 1

Fall lettuce, spinachSow outdoors · Aug 10 – Aug 24

GarlicPlant cloves · Sep 21 – Oct 26

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 11) and first fall frost (Oct 5) 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 99018 came on Mar 23 — 13 days earlier than the 1991–2020 average (Apr 5).

average
Apr 52026
Mar 23

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 6b in Washington

581 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 6b. 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 Latah, WA.

Soil in Latah, WA

The soil mapped at the center of ZIP 99018 is Naff — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.6neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupCwater soaks in slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Naff-Garfield complex, 3 to 15 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 99018; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Latah, WA

Summer high83 °Faverage high, August

Winter low23 °Faverage low, December

Hot days15days a year at 90 °F or more

Freezing nights158nights a year at 32 °F or less

Growing degree days1,748base 50 °F — the season’s usable heat

Longest day15 h 56 mindaylight on June 21

Shortest day8 h 28 mindaylight on December 21

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

Precipitation28.5 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: Plummer 3 Wsw, ID (9 mi away); precipitation: Plummer 3 Wsw, ID (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

Oakesdale, WA · 12 mi

Washington planting zones →

Questions about 99018

What planting zone is ZIP code 99018?

ZIP code 99018 (Latah, WA) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Latah, WA?

The median last spring frost (32 °F) near 99018 is May 11; after June 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Plummer 3 Wsw station.

When is the first frost in Latah, WA?

The median first fall frost near 99018 is October 5, giving a median frost-free growing season of 143 days.

When should I plant tomatoes in 99018?

Start tomato seeds indoors around Mar 16 – Mar 30 and set transplants outside around May 18 – Jun 1, one to three weeks after the median last frost.

How much rain and snow does 99018 get?

About 28.5 inches of precipitation a year (NOAA 1991–2020 normals, Plummer 3 Wsw station).

How hot do summers get in Latah, WA?

The average high peaks at 83 °F in August, with about 15 days a year at 90 °F or more.

What kind of soil does 99018 have?

The USDA soil survey maps Naff at the center of ZIP 99018: silt loam, well drained, pH about 6.6 (neutral).

Did spring come early in Latah, WA in 2026?

Spring leaf-out near 99018 came on Mar 23 in 2026, 13 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Latah, WA?

Long-day onions: the longest day near 99018 is 15 h 56 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).