Washington, D.C. Nature Guide: September 2026
Data updated: August 2026Sources & method · Corrections
September is the District's fall-migration peak — warblers stream back through Rock Creek, broad-winged hawks kettle overhead, and monarchs ride south through the meadows as the markets brim with apples, the last tomatoes, and the first winter squash.
Week by week in September
September 3–9
- Fall migration peaks in Rock Creek with warblers, vireos, and tanagers pouring through after north-wind nights.
- Broad-winged hawks begin kettling south by the hundreds on warm afternoons over the city.
- The first crisp apples from the Blue Ridge orchards arrive alongside the last summer tomatoes.
September 10–16
- The migratory monarch generation streams south through the city, fueling on goldenrod and asters in the meadows.
- Sharp-shinned and Cooper's hawks move overhead, and common nighthawks stream over the city at dusk.
- New England and aromatic asters add rich purple to the meadows at their fall peak.
September 17–23
- The autumn equinox around September 22 brings equal day and night, with Pegasus and Andromeda climbing the east.
- Plant garlic and shallots and set out new perennials, trees, and shrubs in the still-warm soil.
- Black gum and sourwood flame deep scarlet and the sassafras begins turning orange in the understory.
September 24–30
- Sparrow migration builds with white-throated sparrows and the first dark-eyed juncos filling the brushy edges.
- Acorns and hickory nuts rain down across Rock Creek, feeding squirrels, jays, and woodpeckers.
- Winter squash, pumpkins, and grapes arrive as the last summer fruit lingers at the markets.
Birds This Month
September is one of the District's two best birding months as fall migration peaks. Rock Creek Park fills again with warblers — American redstart, magnolia, black-throated blue and green, chestnut-sided, Cape May, bay-breasted, Tennessee, and the abundant blackpoll — plus red-eyed vireos, scarlet tanagers, rose-breasted grosbeaks, and migrant thrushes. Mixed flocks move through the ravine all morning after a north-wind night.
Overhead, broad-winged hawks kettle south by the hundreds on warm afternoons, followed by Cooper's and sharp-shinned hawks, ospreys, and Bald Eagles. Common nighthawks stream over the city at dusk, ruby-throated hummingbirds peak at the jewelweed, and southbound shorebirds still work the Anacostia mudflats.
This month's tip: bird Rock Creek at dawn after a cold front with north winds for the densest warbler flocks, then watch the afternoon sky for kettles of broad-winged hawks riding the thermals south.
What's Blooming
September is the District's great month of fall bloom. The meadows and roadsides blaze with goldenrods of many species and the rich purples and lavenders of New England and New York asters, aromatic aster, and calico aster, alongside ironweed, Joe-Pye weed, sneezeweed, boneset, and wingstem — the crucial late nectar for migrating monarchs at the Arboretum and Kenilworth meadows.
In the moist woods and along the rivers, jewelweed, great blue lobelia, turtlehead, cardinal flower, and white snakeroot bloom in the shade, and the tidal marshes still hold swamp rose mallow and tickseed sunflower glowing yellow. Sunny fields keep partridge pea, black-eyed Susan, and thoroughwort, and the District's gardens carry late asters, anemones, sedum, and the persistent American Beauty roses into autumn.
Garden This Month
September is the District's prime fall-planting and transition month. The cool-season garden takes over as the heat breaks: keep sowing spinach, lettuce, arugula, mâche, radishes, and quick greens, and tend the broccoli, cabbage, kale, and collards set out in late summer, which sweeten as the nights cool. The last tomatoes, peppers, okra, and eggplant ripen on, and warm-season crops wind down.
This is the best time to plant or renovate the lawn and to set out new perennials, trees, and shrubs, which root well in the still-warm soil and cooling air. Toward month's end, plant garlic and shallots for next summer. Pull spent plants, add compost, sow cover crops on empty beds, and dig and store sweet potatoes before the first frost. Save seed from your best open-pollinated plants, and start bringing in tender potted herbs.
Zone 7a (cooler uplands and Rock Creek corridor): keep harvesting fall greens and roots and sow a final quick round of spinach and lettuce under cover. Plant garlic late in the month, and protect tender crops if an early frost threatens.
Zone 7b (warmer downtown and riverside core): the long warm fall lets you keep sowing greens and radishes well into the month. The last tomatoes and peppers ripen on, and garlic can go in toward month's end.
What's at the Farmers Market
September markets in D.C. straddle summer and fall. The last tomatoes, peppers, eggplant, okra, sweet corn, and melons overlap with the season's first apples and pears from the Blue Ridge orchards and the earliest winter squash — acorn, delicata, butternut, and spaghetti — at Eastern Market and the FreshFarm stalls.
Grapes, late peaches, Asian pears, broccoli, cauliflower, greens, and the first fall spinach and lettuce arrive, and Chesapeake blue crabs stay strong into early fall. Choose apples that are firm and heavy with no soft spots and store them cold; pick winter squash that feels hard and heavy with a dry, corky stem and keep it cool and dry rather than refrigerated. Grab the last summer fruit while it lasts — the markets are tipping toward the harvest season.
The Washington, D.C. native plants guide covers what grows here
Night Sky This Month
September balances the District's sky at the autumn equinox around September 22, bringing equal day and night and earlier, cooler evenings for stargazing. The Summer Triangle of Vega, Deneb, and Altair still rides high after dusk, but the autumn stars climb in the east — the great square of Pegasus and the chained figure of Andromeda.
From Andromeda you can find the Andromeda Galaxy, the most distant object visible to the naked eye, a faint smudge under truly dark skies and an easy target in binoculars. There's no major meteor shower this month, so September is for the rising autumn constellations and the lingering summer Milky Way in the west — both best from beyond the city's light.
Drive into the rural Maryland or Virginia countryside for the darkest views. The printable Washington, D.C. night-sky guide gives this year's planet positions for the District.
Butterflies & Pollinators
September is the District's monarch month. The migratory monarch generation streams south through the city, riding cold fronts and stopping to nectar on the goldenrod, ironweed, and asters of the Arboretum and Kenilworth meadows — the single most important fall-fueling event for the District's butterflies. They are joined by the year's last broods of eastern tiger and other swallowtails, great spangled fritillaries, common buckeyes (now abundant), red admirals, painted and American ladies, clouded and orange sulphurs, and clouds of skippers on the late blooms. Sleepy oranges and fiery skippers may push north in good years. Watch a sunny meadow on a clear afternoon for southbound monarchs feeding and gliding through. Leave the late goldenrod and asters standing and unmowed — they are the fuel stops that carry the monarchs on toward Mexico.
What to plant for them is in the Washington, D.C. native plants guide
Trees This Month
September begins the District's autumn turn. The earliest changers lead the way: black gum (tupelo) and sourwood flame deep scarlet, flowering dogwoods redden and set clusters of red berries, and sumacs blaze crimson along the wood edges and roadsides. The sassafras begins turning orange, apricot, and red in the understory, and the black walnuts drop their yellowing leaves and heavy nuts early.
The mast crop falls in earnest: acorns rain from the scarlet, white, and red oaks, hickory nuts and black walnuts hit the ground, feeding squirrels, jays, and woodpeckers. The big canopy trees — tulip tree, oaks, maples, and the Mall elms — are still mostly green but tinged with the first yellow. Cooler nights and shortening days are setting the stage for the brilliant October color to come across Rock Creek and the city's hills.
The Washington, D.C. native plants guide covers what grows with them
Weather & Daylight
Across Washington, D.C., a typical September day averages a high near 78°F and a low near 58°F, with about 4.3 inches of precipitation — District-wide averages from the 1991–2020 U.S. climate normals.
Summer eases gradually, still warm upper-70s days and mild high-50s nights, though heavy rain keeps the air heavy.
| Average high | 78°F |
|---|---|
| Average low | 58°F |
| Precipitation | 4.3 in |
| Sunrise (mid-month) | 6:49 ET |
| Sunset (mid-month) | 19:18 ET |
Figures are District-wide 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 (ET). Temperature and precipitation use Maryland District-wide normals (the District has no separate climate series).
Next month's version of this page, by email
One short note when Washington, D.C.'s next month turns — what's arriving, blooming, and worth a night outside.
Go deeper with the Washington, D.C. guides
The complete Washington, D.C. birding, native-plant, and night-sky references — or the whole year, week by week, in one book.
Same month elsewhere: September in Florida · September in Georgia · September in Idaho