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

Planting zone for 99166 — Republic, WA

ZIP code 99166 (Republic, Ferry County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 30 and the first fall frost September 10.

Where ZIP 99166 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostMay 30

First frostSep 10

2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Republic, 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 Republic, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 30median — 50% chance of a later frost

Safe for tender plantsJune 17only 10% chance of frost after

First fall frostSeptember 10median — 10% chance by Aug 28

Growing season102 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 12 and returns around September 24.

From the NOAA station Republic, WA — 4 miles away, elevation 2,556 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 99166

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 18 – May 2

SpinachSow outdoors · Apr 18 – May 9

Broccoli, cabbageStart indoors · Mar 21 – Apr 4

Broccoli, cabbageTransplant · May 9 – May 23

Onion setsPlant outdoors · May 2 – May 16

PotatoesPlant outdoors · May 9 – May 23

LettuceSow outdoors · May 2 – May 16

Carrots, beetsSow outdoors · May 9 – May 23

TomatoesStart indoors · Apr 4 – Apr 18

TomatoesTransplant · Jun 6 – Jun 20

Peppers, eggplantStart indoors · Mar 21 – Apr 4

Peppers, eggplantTransplant · Jun 13 – Jun 27

BeansSow outdoors · Jun 6 – Jun 20

Sweet cornSow outdoors · Jun 6 – Jun 20

Cucumbers, squashSow outdoors · Jun 6 – Jun 20

Fall lettuce, spinachSow outdoors · Jul 16 – Jul 30

GarlicPlant cloves · Aug 27 – Oct 1

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 30) and first fall frost (Sep 10) 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 99166 came on Apr 18 — about the same time as the 1991–2020 average (Apr 20).

average
Apr 202026
Apr 18

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 6a in Washington

576 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 Republic, WA.

Soil in Republic, WA

The soil mapped at the center of ZIP 99166 is Nevine — loam, well drained.

TextureLoama good balance for most vegetables

pH6.7neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Nevine loam, 30 to 45 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 99166; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Republic, WA

Summer high84 °Faverage high, July

Winter low16 °Faverage low, January

Hot days18days a year at 90 °F or more

Freezing nights188nights a year at 32 °F or less

Growing degree days1,547base 50 °F — the season’s usable heat

Longest day16 h 08 mindaylight on June 21

Shortest day8 h 17 mindaylight on December 21

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

Precipitation18.1 inper year, rain and melted snow

Snowfall53 inper year; 100 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

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

Nearby ZIP codes

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

Kettle Falls, WA · 24 mi

Washington planting zones →

Questions about 99166

What planting zone is ZIP code 99166?

ZIP code 99166 (Republic, WA) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Republic, WA?

The median last spring frost (32 °F) near 99166 is May 30; after June 17 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Republic station.

When is the first frost in Republic, WA?

The median first fall frost near 99166 is September 10, giving a median frost-free growing season of 102 days.

When should I plant tomatoes in 99166?

Start tomato seeds indoors around Apr 4 – Apr 18 and set transplants outside around Jun 6 – Jun 20, one to three weeks after the median last frost.

How much rain and snow does 99166 get?

About 18.1 inches of precipitation a year and 53 inches of snowfall (NOAA 1991–2020 normals, Republic station).

How hot do summers get in Republic, WA?

The average high peaks at 84 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 99166 have?

The USDA soil survey maps Nevine at the center of ZIP 99166: loam, well drained, pH about 6.7 (neutral).

Did spring come early in Republic, WA in 2026?

Spring leaf-out near 99166 came on Apr 18 in 2026, about the same as the 1991–2020 average (Apr 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Republic, WA?

Long-day onions: the longest day near 99166 is 16 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99166 change?

Yes. The 2012 USDA map put 99166 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.