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

Planting zone for 98233 — Burlington, WA

ZIP code 98233 (Burlington, Skagit County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is March 24 and the first fall frost November 3.

Where ZIP 98233 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 frostMar 24
First frostNov 3
2012 zone8b

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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Burlington, 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 Burlington, WA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 24median — 50% chance of a later frost
Safe for tender plantsApril 14only 10% chance of frost after
First fall frostNovember 3median — 10% chance by Oct 12
Growing season224 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 27 and returns around November 25.

From the NOAA station Mt Vernon 3 Wnw, WA — 4 miles away, elevation 13 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 98233

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 10 – Feb 24
SpinachSow outdoors · Feb 10 – Mar 3
Broccoli, cabbageStart indoors · Jan 13 – Jan 27
Broccoli, cabbageTransplant · Mar 3 – Mar 17
Onion setsPlant outdoors · Feb 24 – Mar 10
PotatoesPlant outdoors · Mar 3 – Mar 17
LettuceSow outdoors · Feb 24 – Mar 10
Carrots, beetsSow outdoors · Mar 3 – Mar 17
TomatoesStart indoors · Jan 27 – Feb 10
TomatoesTransplant · Mar 31 – Apr 14
Peppers, eggplantStart indoors · Jan 13 – Jan 27
Peppers, eggplantTransplant · Apr 7 – Apr 21
BeansSow outdoors · Mar 31 – Apr 14
Sweet cornSow outdoors · Mar 31 – Apr 14
Cucumbers, squashSow outdoors · Mar 31 – Apr 14
Fall lettuce, spinachSow outdoors · Sep 8 – Sep 22
GarlicPlant cloves · Oct 20 – Nov 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 24) and first fall frost (Nov 3) 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 98233 came on Feb 17 — 3 days earlier than the 1991–2020 average (Feb 20).

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).

Soil in Burlington, WA

The soil mapped at the center of ZIP 98233 is Sumas — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter6%high
Hydrologic groupCwater soaks in slowly
Farmland classPrime farmland if drainedUSDA classification

Map unit: Sumas silt loam.

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 98233; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Burlington, WA

Summer high75 °Faverage high, August
Winter low35 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights46nights a year at 32 °F or less
Growing degree days1,764base 50 °F — the season’s usable heat
Longest day16 h 07 mindaylight on June 21
Shortest day8 h 18 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation48.5 inper year, rain and melted snow
Snowfall6 inper year; 4 days with snow on the ground

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 47 °F, low 35 °F 47°35° JanFebruary: average high 50 °F, low 35 °F 50°35° FebMarch: average high 54 °F, low 38 °F 54°38° MarApril: average high 58 °F, low 41 °F 58°41° AprMay: average high 65 °F, low 47 °F 65°47° MayJune: average high 69 °F, low 51 °F 69°51° JunJuly: average high 73 °F, low 54 °F 73°54° JulAugust: average high 75 °F, low 53 °F 75°53° AugSeptember: average high 69 °F, low 49 °F 69°49° SepOctober: average high 59 °F, low 43 °F 59°43° OctNovember: average high 51 °F, low 39 °F 51°39° NovDecember: average high 46 °F, low 35 °F 46°35° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″8″January: 6.18 in precipitation, 0.6 in snowfall 6.2❄1 JanFebruary: 4.11 in precipitation, 0.2 in snowfall 4.1 FebMarch: 4.76 in precipitation, 0.4 in snowfall 4.8 MarApril: 4.17 in precipitation 4.2 AprMay: 3.46 in precipitation 3.5 MayJune: 2.60 in precipitation 2.6 JunJuly: 1.34 in precipitation 1.3 JulAugust: 1.60 in precipitation 1.6 AugSeptember: 2.86 in precipitation 2.9 SepOctober: 4.98 in precipitation, 0.1 in snowfall 5.0 OctNovember: 7.02 in precipitation, 0.7 in snowfall 7.0❄1 NovDecember: 5.45 in precipitation, 3.7 in snowfall 5.5❄4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mt Vernon 3 Wnw, WA (4 mi away); precipitation: Sedro-Woolley, WA (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 8b.

982328b
Bow, WA · 5 mi
982358b
Clearlake, WA · 6 mi
982738b
Mount Vernon, WA · 7 mi
982578b
La Conner, WA · 10 mi
982848b
Sedro Woolley, WA · 10 mi
982388b
Conway, WA · 11 mi
982218b
Anacortes, WA · 12 mi
982638b
Lyman, WA · 13 mi

Washington planting zones →

Questions about 98233

What planting zone is ZIP code 98233?

ZIP code 98233 (Burlington, 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 Burlington, WA?

The median last spring frost (32 °F) near 98233 is March 24; after April 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mt Vernon 3 Wnw station.

When is the first frost in Burlington, WA?

The median first fall frost near 98233 is November 3, giving a median frost-free growing season of 224 days.

When should I plant tomatoes in 98233?

Start tomato seeds indoors around Jan 27 – Feb 10 and set transplants outside around Mar 31 – Apr 14, one to three weeks after the median last frost.

How much rain and snow does 98233 get?

About 48.5 inches of precipitation a year and 6 inches of snowfall (NOAA 1991–2020 normals, Sedro-Woolley station).

How hot do summers get in Burlington, WA?

The average high peaks at 75 °F in August, with about 0 days a year at 90 °F or more.

What kind of soil does 98233 have?

The USDA soil survey maps Sumas at the center of ZIP 98233: silt loam, poorly drained, pH about 6.7 (neutral).

Did spring come early in Burlington, WA in 2026?

Spring leaf-out near 98233 came on Feb 17 in 2026, 3 days earlier than the 1991–2020 average (Feb 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Burlington, WA?

Long-day onions: the longest day near 98233 is 16 h 07 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).