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

Planting zone for 98320 — Brinnon, WA

ZIP code 98320 (Brinnon, Jefferson County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 11 and the first fall frost October 28.

Where ZIP 98320 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.

Zone8b15 to 20 °F

Coldest night−9.4 to −6.7 °C

Last frostApr 11

First frostOct 28

2012 zone8a

Was 8a 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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Brinnon, 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 Brinnon, WA

JanFebMarAprMayJunJulAugSepOctNovDec

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

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

Safe for tender plantsMay 1only 10% chance of frost after

First fall frostOctober 28median — 10% chance by Oct 13

Growing season199 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 7 and returns around November 15.

From the NOAA station Quilcene 2 Sw, WA — 10 miles away, elevation 125 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 98320

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 28 – Mar 14

SpinachSow outdoors · Feb 28 – Mar 21

Broccoli, cabbageStart indoors · Jan 31 – Feb 14

Broccoli, cabbageTransplant · Mar 21 – Apr 4

Onion setsPlant outdoors · Mar 14 – Mar 28

PotatoesPlant outdoors · Mar 21 – Apr 4

LettuceSow outdoors · Mar 14 – Mar 28

Carrots, beetsSow outdoors · Mar 21 – Apr 4

TomatoesStart indoors · Feb 14 – Feb 28

TomatoesTransplant · Apr 18 – May 2

Peppers, eggplantStart indoors · Jan 31 – Feb 14

Peppers, eggplantTransplant · Apr 25 – May 9

BeansSow outdoors · Apr 18 – May 2

Sweet cornSow outdoors · Apr 18 – May 2

Cucumbers, squashSow outdoors · Apr 18 – May 2

Fall lettuce, spinachSow outdoors · Sep 2 – Sep 16

GarlicPlant cloves · Oct 14 – Nov 18

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 11) and first fall frost (Oct 28) 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 98320 came on Apr 3 — 21 days earlier than the 1991–2020 average (Apr 24).

average
Apr 242026
Apr 3

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 8b in Washington

614 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive 15 °F or colder — the bottom of zone 8b. 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 Brinnon, WA.

Soil in Brinnon, WA

The soil mapped at the center of ZIP 98320 is Haplocryands — extremely gravelly sandy loam, well drained.

TextureExtremely gravelly sandy loamdrains and warms fast; dries out and needs more feeding

pH4.5strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter8.5%high

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Rock outcrop-Haplocryands association, glacial trough, 60 to 100 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 98320; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Brinnon, WA

Summer high77 °Faverage high, July

Winter low32 °Faverage low, January

Hot days5days a year at 90 °F or more

Freezing nights83nights a year at 32 °F or less

Growing degree days1,769base 50 °F — the season’s usable heat

Longest day16 h 00 mindaylight on June 21

Shortest day8 h 25 mindaylight on December 21

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

Precipitation76.4 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: Quilcene 2 Sw, WA (10 mi away); precipitation: Mount Crag, WA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 8b.

983808b

Seabeck, WA · 10 mi

985558b

Lilliwaup, WA · 11 mi

985488b

Hoodsport, WA · 12 mi

983768b

Quilcene, WA · 14 mi

983128b

Bremerton, WA · 16 mi

Washington planting zones →

Questions about 98320

What planting zone is ZIP code 98320?

ZIP code 98320 (Brinnon, WA) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Brinnon, WA?

The median last spring frost (32 °F) near 98320 is April 11; after May 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Quilcene 2 Sw station.

When is the first frost in Brinnon, WA?

The median first fall frost near 98320 is October 28, giving a median frost-free growing season of 199 days.

When should I plant tomatoes in 98320?

Start tomato seeds indoors around Feb 14 – Feb 28 and set transplants outside around Apr 18 – May 2, one to three weeks after the median last frost.

How much rain and snow does 98320 get?

About 76.4 inches of precipitation a year (NOAA 1991–2020 normals, Mount Crag station).

How hot do summers get in Brinnon, WA?

The average high peaks at 77 °F in July, with about 5 days a year at 90 °F or more.

What kind of soil does 98320 have?

The USDA soil survey maps Haplocryands at the center of ZIP 98320: extremely gravelly sandy loam, well drained, pH about 4.5 (strongly acidic).

Did spring come early in Brinnon, WA in 2026?

Spring leaf-out near 98320 came on Apr 3 in 2026, 21 days earlier than the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Brinnon, WA?

Long-day onions: the longest day near 98320 is 16 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 98320 change?

Yes. The 2012 USDA map put 98320 in zone 8a; the 2023 map puts it in zone 8b. The newer map uses 1991–2020 data and more weather stations.