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

Planting zone for Lake Oswego, OR

Lake Oswego, OR is in USDA zone 9a across its 2 ZIP codes. The median last spring frost is March 18 and the first fall frost November 18.

Lake Oswego 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.

Zone9a20 to 25 °F
ZIP codes2
Last frostMar 18
First frostNov 18
Growing season244 days

9a 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Lake Oswego, OR…

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 Lake Oswego, OR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 18median — 50% chance of a later frost
Safe for tender plantsApril 11only 10% chance of frost after
First fall frostNovember 18median — 10% chance by Oct 30
Growing season244 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 12 and returns around December 8.

From the NOAA station Oregon City, OR, elevation 167 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 Lake Oswego

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 4 – Feb 18
SpinachSow outdoors · Feb 4 – Feb 25
Broccoli, cabbageStart indoors · Jan 7 – Jan 21
Broccoli, cabbageTransplant · Feb 25 – Mar 11
Onion setsPlant outdoors · Feb 18 – Mar 4
PotatoesPlant outdoors · Feb 25 – Mar 11
LettuceSow outdoors · Feb 18 – Mar 4
Carrots, beetsSow outdoors · Feb 25 – Mar 11
TomatoesStart indoors · Jan 21 – Feb 4
TomatoesTransplant · Mar 25 – Apr 8
Peppers, eggplantStart indoors · Jan 7 – Jan 21
Peppers, eggplantTransplant · Apr 1 – Apr 15
BeansSow outdoors · Mar 25 – Apr 8
Sweet cornSow outdoors · Mar 25 – Apr 8
Cucumbers, squashSow outdoors · Mar 25 – Apr 8
Fall lettuce, spinachSow outdoors · Sep 23 – Oct 7
GarlicPlant cloves · Nov 4 – Dec 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 18) and first fall frost (Nov 18) 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 97035 came on Feb 14 — about the same time as the 1991–2020 average (Feb 16).

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 9a in Oregon

666 plants native to the lower 48 states, recorded in Oregon, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. Each links to its USDA PLANTS profile.

Trees 44

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 °FBishop pine90 ft · blooms mid spring · low shade tolerance · to 17 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °F

Shrubs 133

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 169

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 Lake Oswego, OR.

Soil in Lake Oswego, OR

The soil mapped at the center of ZIP 97035 is Xerochrepts — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables
pH5.6moderately acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Xerochrepts-Rock outcrop complex, moderately steep.

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 97035; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Lake Oswego, OR

Summer high82 °Faverage high, July
Winter low34 °Faverage low, January
Hot days15days a year at 90 °F or more
Freezing nights42nights a year at 32 °F or less
Growing degree days2,459base 50 °F — the season’s usable heat
Longest day15 h 40 mindaylight on June 21
Shortest day8 h 43 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation45.3 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 49 °F, low 34 °F 49°34° JanFebruary: average high 53 °F, low 35 °F 53°35° FebMarch: average high 58 °F, low 37 °F 58°37° MarApril: average high 64 °F, low 40 °F 64°40° AprMay: average high 70 °F, low 46 °F 70°46° MayJune: average high 75 °F, low 50 °F 75°50° JunJuly: average high 82 °F, low 54 °F 82°54° JulAugust: average high 82 °F, low 54 °F 82°54° AugSeptember: average high 77 °F, low 50 °F 77°50° SepOctober: average high 65 °F, low 43 °F 65°43° OctNovember: average high 54 °F, low 38 °F 54°38° NovDecember: average high 48 °F, low 34 °F 48°34° Dec

Precipitation by month inches

0″2″4″6″8″January: 6.41 in precipitation 6.4 JanFebruary: 4.71 in precipitation 4.7 FebMarch: 5.47 in precipitation 5.5 MarApril: 3.82 in precipitation 3.8 AprMay: 2.67 in precipitation 2.7 MayJune: 1.68 in precipitation 1.7 JunJuly: 0.50 in precipitation 0.5 JulAugust: 0.53 in precipitation 0.5 AugSeptember: 1.53 in precipitation 1.5 SepOctober: 3.87 in precipitation 3.9 OctNovember: 6.34 in precipitation 6.3 NovDecember: 7.73 in precipitation 7.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Beaverton 2 Ssw, OR (6 mi away); precipitation: Raleigh Hills 2.1 Ese, OR (4 mi away). Daylight is calculated from latitude.

ZIP codes in Lake Oswego

970349a
20 to 25 °F
970359a
20 to 25 °F

Oregon planting zones →

Questions about Lake Oswego

What planting zone is Lake Oswego, OR?

Lake Oswego, OR is in USDA hardiness zone 9a on the 2023 map (9a: 20 to 25 °F).

When is the last frost in Lake Oswego, OR?

The median last spring frost is March 18 and the median first fall frost is November 18 (NOAA 1991–2020 normals, Oregon City station).

When can I plant a garden in Lake Oswego, OR?

Cool-season crops like peas and spinach go in around Feb 4 – Feb 25; tomatoes, peppers, beans and squash after about Mar 25, once frost risk has passed.

What kind of onions grow in Lake Oswego, OR?

Long-day onions: the longest day is 15 h 40 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Lake Oswego, OR get?

About 45.3 inches of precipitation a year (NOAA 1991–2020 normals).