September in Nature: What to Look For Across the U.S.
Happening nowSeptember is fall migration's main act: warblers and other songbirds stream south all month, hawk-watching season peaks with kettles of broad-winged hawks mid-month, and hummingbirds depart the northern states. Goldenrod and asters hit their full peak. No major meteor shower peaks in September; the equinox around the 22nd evens day and night.
Data updated: August 2026Sources & method · Corrections
September is spring migration run in reverse, at greater volume and half the fanfare. Every songbird that pushed north in April and May comes back through in September — plus the summer's young — but in muted plumage and near silence, which is why the season belongs to people paying attention: mixed flocks working through the trees on a cool morning after a north-wind front, flight calls overhead at night, sudden yard birds that weren't there yesterday. Mid-month brings the year's most concentrated raptor spectacle, as broad-winged hawks funnel south in swirling kettles that can number in the thousands at the classic hawk-watch ridges and lakeshores. Hummingbirds leave the top of the map first: most depart the northern tier in early September, the Mid-Atlantic by month's end — feeders should stay up a couple of weeks past your last sighting for the stragglers coming through behind. The fields, meanwhile, are at their late peak: goldenrod and aster season crests in September, monarchs ride it south, and the first cold nights put the year's turn in writing.
Bird migration
Songbird migration peaks across most of the country — warblers, vireos, thrushes, and flycatchers moving nightly, best seen on mornings after cold fronts. Broad-winged hawk flights crest in mid-September, the biggest single-day raptor counts of the year at established watch sites. Shorebird migration continues with juveniles now dominating, hummingbirds clear the northern states, and by late month the first sparrows and waterfowl of the fall arrive from the north. The whole month is motion.
What's blooming
Peak aster-and-goldenrod season: New England aster, the white woodland asters, and a half-dozen goldenrods carry fields, roadsides, and gardens through the month — the last broad nectar source of the year, and the fuel line for the monarch migration passing through nearly every state. In the West, rabbitbrush golds the sagebrush country. First frost ends the show early in the mountains and the far northern tier.
In the night sky
No major meteor shower peaks in September — the month's sky story is the balance point: the autumn equinox around the 22nd, after which nights outlast days for the next six months. Darkness arrives noticeably earlier each week, which quietly reopens casual stargazing after the short nights of summer, and the month's full moon — the Harvest Moon, nearest the equinox — rises at dusk several evenings running.
In the garden
September is the best planting month most gardeners skip: warm soil and cooling air make it ideal for perennials, shrubs, trees, and cool-season crops in most regions, and it opens bulb-planting season in the North. Harvest continues at full tilt — winter squash and the main tomato crop come in ahead of first frost in the mid-latitudes. Let the goldenrod and asters stand; they're working until the frost puts them down.
The September sky, 2026
The moon in September: New moon Sep 10 · Full moon Sep 26. Darkest skies fall around Sep 5–Sep 15, near the new moon.
September in every state
The month ahead, by email
One short note a month. Nothing else.