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

Planting zone for 97603 — Klamath Falls, OR

ZIP code 97603 (Klamath Falls, Klamath County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is June 9 and the first fall frost September 18.

Where ZIP 97603 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.

Zone6b−5 to 0 °F
Coldest night−20.6 to −17.8 °C
Last frostJun 9
First frostSep 18
2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Klamath Falls, 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 Klamath Falls, OR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 9median — 50% chance of a later frost
Safe for tender plantsJune 26only 10% chance of frost after
First fall frostSeptember 18median — 10% chance by Sep 4
Growing season99 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 21 and returns around October 2.

From the NOAA station Klamath Falls Intl Airport, OR — 3 miles away, elevation 4,085 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 97603

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 28 – May 12
SpinachSow outdoors · Apr 28 – May 19
Broccoli, cabbageStart indoors · Mar 31 – Apr 14
Broccoli, cabbageTransplant · May 19 – Jun 2
Onion setsPlant outdoors · May 12 – May 26
PotatoesPlant outdoors · May 19 – Jun 2
LettuceSow outdoors · May 12 – May 26
Carrots, beetsSow outdoors · May 19 – Jun 2
TomatoesStart indoors · Apr 14 – Apr 28
TomatoesTransplant · Jun 16 – Jun 30
Peppers, eggplantStart indoors · Mar 31 – Apr 14
Peppers, eggplantTransplant · Jun 23 – Jul 7
BeansSow outdoors · Jun 16 – Jun 30
Sweet cornSow outdoors · Jun 16 – Jun 30
Cucumbers, squashSow outdoors · Jun 16 – Jun 30
Fall lettuce, spinachSow outdoors · Jul 24 – Aug 7
GarlicPlant cloves · Sep 4 – Oct 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 9) and first fall frost (Sep 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 97603 came on Mar 17 — 22 days earlier than the 1991–2020 average (Apr 8).

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 6b in Oregon

613 plants native to the lower 48 states, recorded in Oregon, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Trees 40

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 114

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 287

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 161

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 Klamath Falls, OR.

Soil in Klamath Falls, OR

The soil mapped at the center of ZIP 97603 is Lorella — very stony loam, well drained.

TextureVery stony loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Lorella-Calimus association, steep north 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 97603; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Klamath Falls, OR

Summer high86 °Faverage high, July
Winter low21 °Faverage low, December
Hot days18days a year at 90 °F or more
Freezing nights184nights a year at 32 °F or less
Growing degree days1,747base 50 °F — the season’s usable heat
Longest day15 h 15 mindaylight on June 21
Shortest day9 h 06 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation11.1 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 42 °F, low 22 °F 42°22° JanFebruary: average high 46 °F, low 24 °F 46°24° FebMarch: average high 52 °F, low 27 °F 52°27° MarApril: average high 58 °F, low 29 °F 58°29° AprMay: average high 67 °F, low 36 °F 67°36° MayJune: average high 76 °F, low 41 °F 76°41° JunJuly: average high 86 °F, low 48 °F 86°48° JulAugust: average high 85 °F, low 47 °F 85°47° AugSeptember: average high 78 °F, low 39 °F 78°39° SepOctober: average high 64 °F, low 31 °F 64°31° OctNovember: average high 49 °F, low 25 °F 49°25° NovDecember: average high 40 °F, low 21 °F 40°21° Dec

Precipitation by month inches

0″1″2″January: 1.51 in precipitation 1.5 JanFebruary: 1.12 in precipitation 1.1 FebMarch: 1.03 in precipitation 1.0 MarApril: 1.06 in precipitation 1.1 AprMay: 1.04 in precipitation 1.0 MayJune: 0.66 in precipitation 0.7 JunJuly: 0.22 in precipitation 0.2 JulAugust: 0.28 in precipitation 0.3 AugSeptember: 0.30 in precipitation 0.3 SepOctober: 0.74 in precipitation 0.7 OctNovember: 1.38 in precipitation 1.4 NovDecember: 1.80 in precipitation 1.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Klamath Falls Intl Airport, OR (3 mi away); precipitation: Klamath Falls Intl Airport, OR (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

976346b
Midland, OR · 7 mi
976336b
Merrill, OR · 9 mi
976026b
Klamath Falls, OR · 9 mi
976256b
Dairy, OR · 13 mi
976326b
Malin, OR · 15 mi
976236b
Bonanza, OR · 19 mi
960236b
Dorris, CA · 22 mi
976396a
Sprague River, OR · 22 mi

All 3 ZIP codes in Klamath Falls → · Oregon planting zones →

Questions about 97603

What planting zone is ZIP code 97603?

ZIP code 97603 (Klamath Falls, OR) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Klamath Falls, OR?

The median last spring frost (32 °F) near 97603 is June 9; after June 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Klamath Falls Intl Airport station.

When is the first frost in Klamath Falls, OR?

The median first fall frost near 97603 is September 18, giving a median frost-free growing season of 99 days.

When should I plant tomatoes in 97603?

Start tomato seeds indoors around Apr 14 – Apr 28 and set transplants outside around Jun 16 – Jun 30, one to three weeks after the median last frost.

How much rain and snow does 97603 get?

About 11.1 inches of precipitation a year (NOAA 1991–2020 normals, Klamath Falls Intl Airport station).

How hot do summers get in Klamath Falls, OR?

The average high peaks at 86 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 97603 have?

The USDA soil survey maps Lorella at the center of ZIP 97603: very stony loam, well drained, pH about 6.7 (neutral).

Did spring come early in Klamath Falls, OR in 2026?

Spring leaf-out near 97603 came on Mar 17 in 2026, 22 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Klamath Falls, OR?

Long-day onions: the longest day near 97603 is 15 h 15 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).