September is the turn — fall migration peaks at the coast and Malheur, the first rains break the summer drought, and the wine-grape harvest gets underway in the Willamette Valley. Vaux's swifts swirl into chimney roosts and the high country begins to color.
Week by week in September
September 3–9
- The coastal estuaries at Bandon Marsh and Coos Bay peak with southbound shorebirds, with rarities turning up among the flocks.
- The first winter squash and a wide range of apples join the last sweet corn, melons, and field tomatoes.
- Plant the overwintering garden now while the soil is warm and newly moist — brassicas, spinach, and the first garlic.
September 10–16
- Thousands of Vaux's swifts swirl into the Chapman School chimney in Portland at dusk — one of the great wildlife shows of the Oregon year.
- Cascade vine maples turn the first flaming red and orange in the forest understory as autumn begins in the high country.
- Around the equinox, the Great Square of Pegasus climbs the east and the Andromeda Galaxy rides high in Oregon's dark-sky country.
September 17–23
- Rabbitbrush blazes at its peak across the high desert, the last great gold of the eastside autumn before winter.
- The first big flocks of cackling and dusky Canada geese and wigeon return to the Willamette Valley refuges.
- Hood River and Gorge pears and apples begin in force; choose pears firm to ripen off the tree at room temperature.
September 24–30
- Sandhill cranes stage in big numbers, and the first wintering Bald Eagles arrive in the Klamath Basin country.
- The first autumn rains revive the moss and ferns on the bigleaf maple limbs as the wet-west forest takes on its lush fall character.
- Oregon's monarchs drift south and west toward their California coastal overwintering groves, closing the small western migration.
Birds This Month
September is one of Oregon's best birding months, with fall migration at full tilt. The coastal estuaries — Bandon Marsh, Coos Bay, the Necanicum — peak with southbound shorebirds: western and least sandpipers, dunlin, dowitchers, plovers, godwits, and red-necked phalaropes, with rarities turning up among them. Offshore, sooty shearwaters and pelagic seabirds stream past, and brown pelicans mass in the bays.
The signature September spectacle is the Vaux's swift roost: thousands of swifts swirl into the Chapman School chimney in Portland at dusk each evening, one of the great wildlife shows of the state. Songbird migration moves through the valley and Malheur — warblers, vireos, tanagers, and flycatchers heading south — and raptor migration builds, with turkey vultures, hawks, and the first returning sandhill cranes. Ruffed grouse have a secondary burst of drumming in the foothills, while sooty grouse move upslope toward their winter range.
What's Blooming
September's bloom is the late, golden flush of Oregon's fall. East of the Cascades, the sagebrush steppe turns gold with rabbitbrush at its blazing peak, drawing late pollinators across the high desert, alongside broom snakeweed and the last asters. In the valley and foothills, goldenrod, asters, gumweed, tarweed, and the late tansy hold on the dry prairies and roadsides.
The coast stays mild and keeps seaside daisy, gumweed, yarrow, and headland flowers going into fall. The high Cascade meadows are nearly finished, but the last gentian, aster, and pearly everlasting linger in sheltered basins. Gardens reach their dahlia-and-aster climax — Willamette Valley dahlia farms are at full glory — with sunflowers, zinnias, and the first colchicum and fall crocus. The first rains green the dry hills again.
Garden This Month
September turns the Oregon garden toward fall and winter. Harvest the last of the warm-season crops — tomatoes, peppers, winter squash, beans, and melons — as the first rains and cooler nights return to the west, and bring in green tomatoes ahead of any cold snap. The defining fall task in mild western Oregon: plant the overwintering garden now while the soil is warm and newly moist.
Set out transplants of broccoli, cabbage, kale, and chard, sow spinach, lettuce, arugula, corn salad, and fava beans, and plant overwintering onions and the first garlic. Sow cover crops like crimson clover and fava on emptying beds. Divide perennials and plant spring bulbs. East of the Cascades, frost arrives now — harvest and store the squash, onions, and potatoes, and plant garlic before the ground freezes around Bend.
Zone 6b (Bend & high desert): first frosts arrive; harvest tender crops ahead of them, plant garlic for next year, and mulch heavily. Pull and store the squash, onions, and potatoes before hard freezes.
Zone 8a (Willamette Valley): harvest the last warm crops and plant for winter. Set out overwintering garlic, onions, and cover crops, sow spinach and corn salad, and divide perennials as the rains return and soil moistens.
Zone 8b (southwest valleys & coast): the long mild fall favors a full winter garden; transplant brassicas, sow lettuce and greens, and plant cover crops. The coast's frost-free autumn keeps greens going for months.
What's at the Farmers Market
September markets bridge summer's bounty and autumn's harvest. The summer crops finish strong — peak tomatoes, peppers, sweet corn, eggplant, and melons — while the fall harvest begins: the first winter squash, apples, Italian prune plums, and early pears. The Willamette Valley wine-grape harvest is underway, and table grapes and fresh juice appear at the stands.
The big event is the start of the pear and apple season from Hood River and the Gorge, and the late blueberries and blackberries hold on. Flower stalls blaze with dahlias and sunflowers. Choose winter squash with a hard rind and intact stem for storage; buy pears firm and let them ripen off the tree at room temperature, and keep apples cold and apart from greens. Store onions and garlic in a cool, dry, airy place. A rich, transitional Oregon market month.
Night Sky This Month
September brings the equinox and crisp, clear nights to Oregon's dark-sky country before the autumn rains build in the west. Pine Mountain Observatory east of Bend runs late-season weekend viewing, and the Oregon Outback International Dark Sky Sanctuary near Lakeview and Prineville Reservoir State Park offer pristine high-desert skies as nights lengthen. The Steens and Cascade lakes still allow late-season dark-sky camping.
The summer Milky Way still arches high after dusk through Cygnus and Sagittarius early in the night, but the autumn stars now rise: the Great Square of Pegasus climbs the east, the Andromeda Galaxy (M31) — the farthest object visible to the naked eye — sits high in dark skies, and the Double Cluster in Perseus follows. There is no major meteor shower in September, making it ideal for the Milky Way, the Andromeda Galaxy, and the bright planets. The printable Oregon night-sky guide gives this year's planet positions and best dark-sky dates.
Butterflies & Pollinators
September's butterflies thin as fall arrives, but warm days still bring activity to Oregon's lowlands. Woodland skippers linger in dry grass, painted ladies, West Coast ladies, and red admirals nectar on the late asters and blooming rabbitbrush, and cabbage whites and orange sulphurs work the gardens and field edges. The last western tiger swallowtails and Lorquin's admirals fly into the month.
Oregon's monarchs are now drifting south and west toward their California coastal overwintering groves — a small but watched western migration. East of the Cascades, the gold rabbitbrush bloom draws a final pulse of coppers, hairstreaks, and blues across the sage steppe. The California tortoiseshells and mourning cloaks that will overwinter as adults seek out sheltered crevices as the nights cool. Leave seed heads, leaf litter, and brush piles for the hibernators and late caterpillars.
Trees This Month
September begins Oregon's long, gradual autumn color, starting in the high country and the east. The Cascade vine maples turn the first flaming red and orange in the forest understory, and the quaking aspen and streamside cottonwoods east of the Cascades and in the Wallowas brighten to gold. The western larch of the eastside forests is still green but weeks from its rare golden-conifer display.
In the valley, the bigleaf maples and Oregon ash begin to yellow along the streams, and the Oregon white oak drops a heavy acorn crop on the savanna. The state tree, Douglas-fir, ripens its cones with their three-pointed bracts. On the coast and southwest hills, the Pacific madrone berries glow orange-red. The first autumn rains revive the moss and ferns on the bigleaf maple limbs, and the wet-west forest takes on its lush, dripping fall character once again.
Weather & Daylight
Across Oregon, a typical September day averages a high near 74°F and a low near 44°F, with about 1.0 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Heat starts to break, mid-70s afternoons and crisp 44-degree nights, with rain picking back up after the dry summer stretch.
| Average high | 74°F |
|---|---|
| Average low | 44°F |
| Precipitation | 1.0 in |
| Sunrise (mid-month) | 6:46 PT |
| Sunset (mid-month) | 19:20 PT |
Figures are statewide averages over the 1991–2020 U.S. climate normals; local conditions vary with elevation and distance from the coast. Sunrise and sunset are computed for a midstate point on the 15th (PT).
Next month's version of this page, by email
One short note when Oregon's next month turns — what's arriving, blooming, and worth a night outside.
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The complete Oregon birding, native-plant, and night-sky references — or the whole year, week by week, in one book.
Same month elsewhere: September in Pennsylvania · September in Rhode Island · September in South Carolina