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

Planting zone for 97883 — Union, OR

ZIP code 97883 (Union, Union County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 11 and the first fall frost September 26.

Where ZIP 97883 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 frostMay 11
First frostSep 26
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 Union, 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 Union, OR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 11median — 50% chance of a later frost
Safe for tender plantsMay 31only 10% chance of frost after
First fall frostSeptember 26median — 10% chance by Sep 9
Growing season136 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 24 and returns around October 7.

From the NOAA station Union, OR — 11 miles away, elevation 2,776 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 97883

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 30 – Apr 13
SpinachSow outdoors · Mar 30 – Apr 20
Broccoli, cabbageStart indoors · Mar 2 – Mar 16
Broccoli, cabbageTransplant · Apr 20 – May 4
Onion setsPlant outdoors · Apr 13 – Apr 27
PotatoesPlant outdoors · Apr 20 – May 4
LettuceSow outdoors · Apr 13 – Apr 27
Carrots, beetsSow outdoors · Apr 20 – May 4
TomatoesStart indoors · Mar 16 – Mar 30
TomatoesTransplant · May 18 – Jun 1
Peppers, eggplantStart indoors · Mar 2 – Mar 16
Peppers, eggplantTransplant · May 25 – Jun 8
BeansSow outdoors · May 18 – Jun 1
Sweet cornSow outdoors · May 18 – Jun 1
Cucumbers, squashSow outdoors · May 18 – Jun 1
Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15
GarlicPlant cloves · Sep 12 – Oct 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 11) and first fall frost (Sep 26) 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 97883 came on Apr 4 — 14 days earlier than the 1991–2020 average (Apr 18).

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 Union, OR.

Soil in Union, OR

The soil mapped at the center of ZIP 97883 is Wonder — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Wonder-Bigcow-Larabee complex, 30 to 60 percent 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 97883; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Union, OR

Summer high87 °Faverage high, August
Winter low25 °Faverage low, January
Hot days29days a year at 90 °F or more
Freezing nights135nights a year at 32 °F or less
Growing degree days2,086base 50 °F — the season’s usable heat
Longest day15 h 38 mindaylight on June 21
Shortest day8 h 45 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation36.3 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 40 °F, low 25 °F 40°25° JanFebruary: average high 45 °F, low 27 °F 45°27° FebMarch: average high 53 °F, low 31 °F 53°31° MarApril: average high 59 °F, low 34 °F 59°34° AprMay: average high 68 °F, low 41 °F 68°41° MayJune: average high 74 °F, low 47 °F 74°47° JunJuly: average high 86 °F, low 51 °F 86°51° JulAugust: average high 87 °F, low 50 °F 87°50° AugSeptember: average high 77 °F, low 43 °F 77°43° SepOctober: average high 63 °F, low 34 °F 63°34° OctNovember: average high 48 °F, low 31 °F 48°31° NovDecember: average high 39 °F, low 25 °F 39°25° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 5.41 in precipitation 5.4 JanFebruary: 4.36 in precipitation 4.4 FebMarch: 4.05 in precipitation 4.0 MarApril: 2.87 in precipitation 2.9 AprMay: 3.01 in precipitation 3.0 MayJune: 2.07 in precipitation 2.1 JunJuly: 0.52 in precipitation 0.5 JulAugust: 0.60 in precipitation 0.6 AugSeptember: 1.11 in precipitation 1.1 SepOctober: 2.21 in precipitation 2.2 OctNovember: 4.28 in precipitation 4.3 NovDecember: 5.78 in precipitation 5.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Union, OR (11 mi away); precipitation: Taylor Green, OR (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

978246b
Cove, OR · 16 mi
978676b
North Powder, OR · 17 mi
978576a
Lostine, OR · 17 mi
978346b
Halfway, OR · 22 mi
978146b
Baker City, OR · 24 mi
978336a
Haines, OR · 25 mi
978416b
Imbler, OR · 27 mi
978506b
La Grande, OR · 28 mi

Oregon planting zones →

Questions about 97883

What planting zone is ZIP code 97883?

ZIP code 97883 (Union, 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 Union, OR?

The median last spring frost (32 °F) near 97883 is May 11; after May 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Union station.

When is the first frost in Union, OR?

The median first fall frost near 97883 is September 26, giving a median frost-free growing season of 136 days.

When should I plant tomatoes in 97883?

Start tomato seeds indoors around Mar 16 – Mar 30 and set transplants outside around May 18 – Jun 1, one to three weeks after the median last frost.

How much rain and snow does 97883 get?

About 36.3 inches of precipitation a year (NOAA 1991–2020 normals, Taylor Green station).

How hot do summers get in Union, OR?

The average high peaks at 87 °F in August, with about 29 days a year at 90 °F or more.

What kind of soil does 97883 have?

The USDA soil survey maps Wonder at the center of ZIP 97883: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Union, OR in 2026?

Spring leaf-out near 97883 came on Apr 4 in 2026, 14 days earlier than the 1991–2020 average (Apr 18), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Union, OR?

Long-day onions: the longest day near 97883 is 15 h 38 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).