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

Planting zone for 97906 — Harper, OR

ZIP code 97906 (Harper, Malheur County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is June 7 and the first fall frost September 6.

Where ZIP 97906 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 7
First frostSep 6
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 Harper, 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 Harper, OR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 7median — 50% chance of a later frost
Safe for tender plantsJune 28only 10% chance of frost after
First fall frostSeptember 6median — 10% chance by Aug 22
Growing season89 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 20 and returns around September 19.

From the NOAA station Riverside 7 Ssw, OR — 20 miles away, elevation 3,379 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 97906

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 26 – May 10
SpinachSow outdoors · Apr 26 – May 17
Broccoli, cabbageStart indoors · Mar 29 – Apr 12
Broccoli, cabbageTransplant · May 17 – May 31
Onion setsPlant outdoors · May 10 – May 24
PotatoesPlant outdoors · May 17 – May 31
LettuceSow outdoors · May 10 – May 24
Carrots, beetsSow outdoors · May 17 – May 31
TomatoesStart indoors · Apr 12 – Apr 26
TomatoesTransplant · Jun 14 – Jun 28
Peppers, eggplantStart indoors · Mar 29 – Apr 12
Peppers, eggplantTransplant · Jun 21 – Jul 5
BeansSow outdoors · Jun 14 – Jun 28
Sweet cornSow outdoors · Jun 14 – Jun 28
Cucumbers, squashSow outdoors · Jun 14 – Jun 28
Fall lettuce, spinachSow outdoors · Jul 12 – Jul 26
GarlicPlant cloves · Aug 23 – Sep 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 7) and first fall frost (Sep 6) 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 97906 came on Mar 23 — 16 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 Harper, OR.

Soil in Harper, OR

The center of ZIP 97906 is mapped as No Digital Data Available: built-over ground without natural soil data. Garden soil here is usually imported or disturbed — test before you plant.

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 97906; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harper, OR

Summer high93 °Faverage high, July
Winter low20 °Faverage low, December
Hot days54days a year at 90 °F or more
Freezing nights195nights a year at 32 °F or less
Growing degree days2,165base 50 °F — the season’s usable heat
Longest day15 h 25 mindaylight on June 21
Shortest day8 h 57 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation8.8 inper year, rain and melted snow
Snowfall6 inper year; 12 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 40 °F, low 21 °F 40°21° JanFebruary: average high 47 °F, low 22 °F 47°22° FebMarch: average high 57 °F, low 27 °F 57°27° MarApril: average high 64 °F, low 30 °F 64°30° AprMay: average high 73 °F, low 37 °F 73°37° MayJune: average high 82 °F, low 43 °F 82°43° JunJuly: average high 93 °F, low 49 °F 93°49° JulAugust: average high 91 °F, low 45 °F 91°45° AugSeptember: average high 82 °F, low 37 °F 82°37° SepOctober: average high 67 °F, low 29 °F 67°29° OctNovember: average high 49 °F, low 23 °F 49°23° NovDecember: average high 39 °F, low 20 °F 39°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.06 in precipitation, 2.1 in snowfall 1.1❄2 JanFebruary: 0.71 in precipitation, 0.6 in snowfall 0.7❄1 FebMarch: 0.77 in precipitation, 0.1 in snowfall 0.8 MarApril: 0.84 in precipitation 0.8 AprMay: 1.14 in precipitation 1.1 MayJune: 0.85 in precipitation 0.8 JunJuly: 0.39 in precipitation 0.4 JulAugust: 0.21 in precipitation 0.2 AugSeptember: 0.40 in precipitation 0.4 SepOctober: 0.54 in precipitation 0.5 OctNovember: 0.77 in precipitation, 0.1 in snowfall 0.8 NovDecember: 1.09 in precipitation, 3.1 in snowfall 1.1❄3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Riverside 7 Ssw, OR (20 mi away); precipitation: Owyhee Dam, OR (31 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

979176a
Riverside, OR · 17 mi
977326a
Crane, OR · 26 mi
979137a
Nyssa, OR · 29 mi
979116a
Juntura, OR · 31 mi
979017a
Adrian, OR · 37 mi
979187a
Vale, OR · 40 mi
979026b
Arock, OR · 41 mi
979206a
Westfall, OR · 42 mi

Oregon planting zones →

Questions about 97906

What planting zone is ZIP code 97906?

ZIP code 97906 (Harper, 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 Harper, OR?

The median last spring frost (32 °F) near 97906 is June 7; after June 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Riverside 7 Ssw station.

When is the first frost in Harper, OR?

The median first fall frost near 97906 is September 6, giving a median frost-free growing season of 89 days.

When should I plant tomatoes in 97906?

Start tomato seeds indoors around Apr 12 – Apr 26 and set transplants outside around Jun 14 – Jun 28, one to three weeks after the median last frost.

How much rain and snow does 97906 get?

About 8.8 inches of precipitation a year and 6 inches of snowfall (NOAA 1991–2020 normals, Owyhee Dam station).

How hot do summers get in Harper, OR?

The average high peaks at 93 °F in July, with about 54 days a year at 90 °F or more.

Did spring come early in Harper, OR in 2026?

Spring leaf-out near 97906 came on Mar 23 in 2026, 16 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harper, OR?

Long-day onions: the longest day near 97906 is 15 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).