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

Planting zone for Hillsboro, OR

Hillsboro, OR is in USDA zone 8b across its 3 ZIP codes. The median last spring frost is April 16 and the first fall frost October 23.

Hillsboro on the zone map

Outlined: its 2 ZIP code areas · 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
ZIP codes3
Last frostApr 16
First frostOct 23
Growing season191 days

8b 3 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 Hillsboro, OR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 16median — 50% chance of a later frost
Safe for tender plantsMay 3only 10% chance of frost after
First fall frostOctober 23median — 10% chance by Oct 3
Growing season191 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 13 and returns around November 12.

From the NOAA station Portland-Hillsboro Airport, OR, elevation 203 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 Hillsboro

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 5 – Mar 19
SpinachSow outdoors · Mar 5 – Mar 26
Broccoli, cabbageStart indoors · Feb 5 – Feb 19
Broccoli, cabbageTransplant · Mar 26 – Apr 9
Onion setsPlant outdoors · Mar 19 – Apr 2
PotatoesPlant outdoors · Mar 26 – Apr 9
LettuceSow outdoors · Mar 19 – Apr 2
Carrots, beetsSow outdoors · Mar 26 – Apr 9
TomatoesStart indoors · Feb 19 – Mar 5
TomatoesTransplant · Apr 23 – May 7
Peppers, eggplantStart indoors · Feb 5 – Feb 19
Peppers, eggplantTransplant · Apr 30 – May 14
BeansSow outdoors · Apr 23 – May 7
Sweet cornSow outdoors · Apr 23 – May 7
Cucumbers, squashSow outdoors · Apr 23 – May 7
Fall lettuce, spinachSow outdoors · Aug 28 – Sep 11
GarlicPlant cloves · Oct 9 – Nov 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 16) and first fall frost (Oct 23) 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 97129 came on Feb 19 — about the same time as 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).

Native plants for zone 8b in Oregon

661 plants native to the lower 48 states, recorded in Oregon, and rated by the USDA to survive 15 °F or colder — the bottom of zone 8b. Each links to its USDA PLANTS profile.

Trees 43

Alaska cedar75 ft · blooms mid spring · low shade tolerance · to −22 °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 °FBrewer spruce100 ft · blooms early summer · low shade tolerance · to −13 °F

Shrubs 132

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °Fbig sagebrush4 ft · blooms mid summer · high shade tolerance · to −43 °F

Wildflowers & perennials 305

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 166

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 2

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °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 Hillsboro, OR.

Soil in Hillsboro, OR

The soil mapped at the center of ZIP 97129 is Dayton — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
pH5.6moderately acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Dayton 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 97129; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Hillsboro, OR

Summer high82 °Faverage high, July
Winter low33 °Faverage low, December
Hot days17days a year at 90 °F or more
Freezing nights64nights a year at 32 °F or less
Growing degree days2,195base 50 °F — the season’s usable heat
Longest day15 h 41 mindaylight on June 21
Shortest day8 h 42 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation35.9 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 47 °F, low 34 °F 47°34° JanFebruary: average high 51 °F, low 34 °F 51°34° FebMarch: average high 56 °F, low 37 °F 56°37° MarApril: average high 61 °F, low 39 °F 61°39° AprMay: average high 69 °F, low 45 °F 69°45° MayJune: average high 74 °F, low 49 °F 74°49° JunJuly: average high 82 °F, low 52 °F 82°52° JulAugust: average high 82 °F, low 52 °F 82°52° AugSeptember: average high 76 °F, low 48 °F 76°48° SepOctober: average high 64 °F, low 41 °F 64°41° OctNovember: average high 53 °F, low 37 °F 53°37° NovDecember: average high 46 °F, low 33 °F 46°33° Dec

Precipitation by month inches

0″2″4″6″January: 5.27 in precipitation 5.3 JanFebruary: 3.97 in precipitation 4.0 FebMarch: 3.70 in precipitation 3.7 MarApril: 2.57 in precipitation 2.6 AprMay: 2.02 in precipitation 2.0 MayJune: 1.31 in precipitation 1.3 JunJuly: 0.37 in precipitation 0.4 JulAugust: 0.48 in precipitation 0.5 AugSeptember: 1.38 in precipitation 1.4 SepOctober: 3.37 in precipitation 3.4 OctNovember: 5.44 in precipitation 5.4 NovDecember: 6.05 in precipitation 6.0 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Portland-Hillsboro Airport, OR (within 1 mile); precipitation: Portland-Hillsboro Airport, OR (within 1 mile). Daylight is calculated from latitude.

ZIP codes in Hillsboro

971238b
15 to 20 °F
971248b
15 to 20 °F
971298b
15 to 20 °F

Oregon planting zones →

Questions about Hillsboro

What planting zone is Hillsboro, OR?

Hillsboro, OR is in USDA hardiness zone 8b on the 2023 map (8b: 15 to 20 °F).

When is the last frost in Hillsboro, OR?

The median last spring frost is April 16 and the median first fall frost is October 23 (NOAA 1991–2020 normals, Portland-Hillsboro Airport station).

When can I plant a garden in Hillsboro, OR?

Cool-season crops like peas and spinach go in around Mar 5 – Mar 26; tomatoes, peppers, beans and squash after about Apr 23, once frost risk has passed.

What kind of onions grow in Hillsboro, OR?

Long-day onions: the longest day is 15 h 41 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Hillsboro, OR get?

About 35.9 inches of precipitation a year (NOAA 1991–2020 normals).