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

Planting zone for 98256 — Index, WA

ZIP code 98256 (Index, Snohomish County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is April 14 and the first fall frost October 29.

Where ZIP 98256 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.

Zone8a10 to 15 °F
Coldest night−12.2 to −9.4 °C
Last frostApr 14
First frostOct 29
2012 zone8a

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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Index, 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 Index, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 14median — 50% chance of a later frost
Safe for tender plantsMay 4only 10% chance of frost after
First fall frostOctober 29median — 10% chance by Oct 12
Growing season197 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 17 and returns around November 19.

From the NOAA station Baring, WA — 5 miles away, elevation 771 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 98256

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 3 – Mar 17
SpinachSow outdoors · Mar 3 – Mar 24
Broccoli, cabbageStart indoors · Feb 3 – Feb 17
Broccoli, cabbageTransplant · Mar 24 – Apr 7
Onion setsPlant outdoors · Mar 17 – Mar 31
PotatoesPlant outdoors · Mar 24 – Apr 7
LettuceSow outdoors · Mar 17 – Mar 31
Carrots, beetsSow outdoors · Mar 24 – Apr 7
TomatoesStart indoors · Feb 17 – Mar 3
TomatoesTransplant · Apr 21 – May 5
Peppers, eggplantStart indoors · Feb 3 – Feb 17
Peppers, eggplantTransplant · Apr 28 – May 12
BeansSow outdoors · Apr 21 – May 5
Sweet cornSow outdoors · Apr 21 – May 5
Cucumbers, squashSow outdoors · Apr 21 – May 5
Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17
GarlicPlant cloves · Oct 15 – Nov 19
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 14) and first fall frost (Oct 29) 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 98256 came on Apr 19 — about the same time as the 1991–2020 average (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 8a in Washington

611 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 8a. 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 113

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 292

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 Index, WA.

Soil in Index, WA

The soil mapped at the center of ZIP 98256 is Typic Vitricryands — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH4.5strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupAwater soaks in fast

Map unit: Typic Vitricryands-Rock outcrop association, 15 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 98256; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Index, WA

Summer high77 °Faverage high, July
Winter low32 °Faverage low, January
Hot days5days a year at 90 °F or more
Freezing nights69nights a year at 32 °F or less
Growing degree days1,767base 50 °F — the season’s usable heat
Longest day16 h 01 mindaylight on June 21
Shortest day8 h 24 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation109.9 inper year, rain and melted snow
Snowfall44 inper year; 43 days with snow on the ground

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 42 °F, low 32 °F 42°32° JanFebruary: average high 47 °F, low 32 °F 47°32° FebMarch: average high 52 °F, low 34 °F 52°34° MarApril: average high 59 °F, low 38 °F 59°38° AprMay: average high 66 °F, low 44 °F 66°44° MayJune: average high 69 °F, low 48 °F 69°48° JunJuly: average high 77 °F, low 52 °F 77°52° JulAugust: average high 77 °F, low 52 °F 77°52° AugSeptember: average high 71 °F, low 48 °F 71°48° SepOctober: average high 58 °F, low 42 °F 58°42° OctNovember: average high 47 °F, low 36 °F 47°36° NovDecember: average high 41 °F, low 32 °F 41°32° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″10″12″14″16″18″January: 16.72 in precipitation, 13.8 in snowfall 16.7❄14 JanFebruary: 10.60 in precipitation, 4.6 in snowfall 10.6❄5 FebMarch: 11.90 in precipitation, 3.8 in snowfall 11.9❄4 MarApril: 8.35 in precipitation, 0.8 in snowfall 8.3❄1 AprMay: 5.02 in precipitation 5.0 MayJune: 3.96 in precipitation 4.0 JunJuly: 1.73 in precipitation 1.7 JulAugust: 1.90 in precipitation 1.9 AugSeptember: 4.79 in precipitation 4.8 SepOctober: 12.30 in precipitation, 0.1 in snowfall 12.3 OctNovember: 18.06 in precipitation, 4.2 in snowfall 18.1❄4 NovDecember: 14.56 in precipitation, 17 in snowfall 14.6❄17 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Baring, WA (5 mi away); precipitation: Baring, WA (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

982248a
Baring, WA · 10 mi
982518a
Gold Bar, WA · 11 mi
982888a
Skykomish, WA · 14 mi
982948b
Sultan, WA · 17 mi
982938b
Startup, WA · 17 mi
982528a
Granite Falls, WA · 22 mi
980148b
Carnation, WA · 22 mi
982728b
Monroe, WA · 22 mi

Washington planting zones →

Questions about 98256

What planting zone is ZIP code 98256?

ZIP code 98256 (Index, WA) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Index, WA?

The median last spring frost (32 °F) near 98256 is April 14; after May 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Baring station.

When is the first frost in Index, WA?

The median first fall frost near 98256 is October 29, giving a median frost-free growing season of 197 days.

When should I plant tomatoes in 98256?

Start tomato seeds indoors around Feb 17 – Mar 3 and set transplants outside around Apr 21 – May 5, one to three weeks after the median last frost.

How much rain and snow does 98256 get?

About 109.9 inches of precipitation a year and 44 inches of snowfall (NOAA 1991–2020 normals, Baring station).

How hot do summers get in Index, 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 98256 have?

The USDA soil survey maps Typic Vitricryands at the center of ZIP 98256: slightly decomposed plant material, well drained, pH about 4.5 (strongly acidic).

Did spring come early in Index, WA in 2026?

Spring leaf-out near 98256 came on Apr 19 in 2026, about the same as the 1991–2020 average (Apr 18), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Index, WA?

Long-day onions: the longest day near 98256 is 16 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).