September is the great turning of the Maine year — hawk and songbird migration in full flood, monarchs streaming down the coast, the first sweep of fall color in the north, and the wild blueberry barrens flushing red. The North Woods begin their famous autumn while the harvest peaks.
Week by week in September
September 3–9
- Hawk migration builds toward its peak — sharp-shinned hawks, ospreys, and kestrels stream past coastal headlands and hilltop hawkwatches.
- Asters and goldenrod blaze across the fields and roadsides, and seaside goldenrod peaks gold on the coastal dunes.
- The first apples arrive and Maine cider presses start running as the orchard harvest begins.
September 10–16
- Broad-winged hawks stream south in spiraling 'kettles' of hundreds or thousands — the peak of the hawk flight, best from Bradbury Mountain and Cadillac.
- Fall color begins sweeping south from the Canadian border — sugar maples flame orange and the birches turn clear gold in the North Woods first.
- Monarch migration is in full flood, funneling down the coast where the land narrows, with roosts forming on calm evenings.
September 17–23
- The autumnal equinox returns longer, darker, cool nights, favorable for aurora in the dark north when geomagnetic activity flares.
- Plant garlic now for next summer and set out spring bulbs, and harvest and cure winter squash and pumpkins ahead of the first frost.
- Monhegan Island becomes a famous fall migrant trap again, drawing rarities and the birders who come to find them.
September 24–30
- The wild lowbush blueberry barrens flush a deep crimson-red across whole Down East hillsides, one of Maine's signature autumn sights.
- Sparrows fill the brushy edges — white-throated, white-crowned, and song — and the last ruby-throated hummingbirds depart for the south.
- The Aroostook potato harvest comes in, and apples, cider, and pumpkins crowd the deep, abundant fall markets.
Birds This Month
September is the second-best birding month in Maine, with fall migration at full flood. The hawk flights peak — broad-winged hawks stream south in spiraling 'kettles' of hundreds or thousands, especially mid-month, joined by sharp-shinned hawks, ospreys, kestrels, and merlins; watch from coastal headlands and hilltop hawkwatches like Bradbury Mountain and Cadillac. Southbound warblers pour through in subtler fall plumage, and Monhegan Island becomes a famous fall migrant trap again, drawing rarities and birders.
The coast hosts the last big shorebird push at Scarborough Marsh and a building movement of sea ducks and loons offshore. Common loons flock and begin molting toward winter gray, Canada geese form their classic Vs, and the last ruby-throated hummingbirds leave by mid-month. Sparrows — white-throated, white-crowned, song, and savannah — fill the brushy edges. Keep feeders stocked; the migrants are moving and fueling up.
What's Blooming
September is the grand finale of Maine's wildflower year, dominated by the asters and the last goldenrods. The roadsides, old fields, and meadows blaze with purple, blue, and white New England aster, heath aster, calico aster, and sky-blue aster, set against the fading gold of goldenrod — together the crucial last nectar for migrating monarchs and late bees. The coastal seaside goldenrod peaks gold on the dunes.
Damp ground holds Joe-Pye weed going to seed, late turtlehead and jewelweed, and a few cardinal flowers. The fields show chicory, yarrow, and lingering Queen Anne's lace. Most striking of all is the foliage turning: the wild lowbush blueberry on the Down East barrens flushes a deep crimson-red across whole hillsides, one of Maine's signature autumn sights. Gardens hold dahlias, sedum, and the last roses. By month's end the first frost ends the bloom in the north.
Garden This Month
September is harvest-and-wind-down in the Maine garden, racing the first frost. Bring in the warm-season crops — tomatoes, peppers, eggplant, beans, corn, cucumbers, and summer squash — and harvest and cure the winter squash, pumpkins, potatoes, and onions for storage. Dig potatoes on a dry day and cure squash in a warm, airy spot before storing. Frost can strike anytime this month in the north and interior, so cover tender crops or pick them ahead of a forecast freeze.
This is the prime month to plant garlic for next summer and to set out spring-flowering bulbs — daffodils, tulips, crocus — as the soil cools. Sow cover crops of winter rye or oats on emptied beds to protect and build the soil, divide and plant perennials while the ground is still warm, and start the fall cleanup. Keep harvesting cold-hardy greens, which sweeten with the first light frosts.
Zone 3b (Aroostook & far north): frost arrives in September here, ending the season. Harvest everything tender before the first hard freeze, dig potatoes, and bring in winter squash to cure — the short northern summer is over.
Zone 4b (interior & mountains): first frost is likely this month. Harvest tomatoes and tender crops ahead of it, plant garlic late in the month, and sow cover crops on cleared beds.
Zone 5b (Midcoast & south): frost usually holds off until late September or October. Keep harvesting, plant garlic and spring bulbs, and sow cover crops as beds empty.
What's at the Farmers Market
September markets are deep and abundant as summer meets fall. The first apples arrive — Maine's orchards begin their harvest now — alongside peak sweet corn, tomatoes, peppers, eggplant, winter squash, pumpkins, potatoes, onions, leeks, carrots, beets, cabbage, broccoli, cauliflower, and fall greens. The last summer raspberries and melons finish, and cranberries begin late in the month.
Maine cider presses start running, and Aroostook potatoes come into their main harvest. Round it out with cheeses, eggs, honey, and meats. Choose apples that are firm and heavy, and store them cold and apart from greens; cure winter squash and pumpkins until the rind is hard and the stem dry, then keep them in a cool, dry room, not the fridge. Store potatoes and onions cool, dark, and ventilated. The markets are at their fullest before the season narrows toward the storage crops of fall.
Night Sky This Month
September brings the autumnal equinox and the welcome return of longer, darker, comfortably cool nights to Maine. The Summer Triangle still rides high after dusk, but the autumn stars take over the east: the Great Square of Pegasus climbs the eastern sky, leading the chain of Andromeda with its famous galaxy — the Andromeda Galaxy (M31), a faint oval to the naked eye from a dark Maine site and lovely in binoculars. The Milky Way still arches overhead on moonless nights.
There is no major meteor shower this month, but the crisp, clear autumn air and the elimination of summer's haze and bugs make for excellent stargazing. Around the equinox, Maine's dark north is statistically favored for aurora displays when geomagnetic activity flares. The cool, transparent nights at Acadia, Baxter, and the North Woods are superb. The printable Maine night-sky guide lists this year's planet positions, aurora outlook, and the best dark-sky dates around the new moon.
Butterflies & Pollinators
September is monarch migration month in Maine, the great natural spectacle of the late season. The migratory generation of monarchs streams south, funneling down the coast and concentrating along the shore where the land narrows; on a good day with north winds you can watch them drifting past coastal points by the dozens or hundreds, stopping to nectar on the abundant goldenrod and asters that fuel their journey to Mexico. Coastal roosts form on calm evenings.
The rest of the butterfly community is winding down but still active on warm afternoons. Painted ladies, red admirals, American ladies, question marks, and commas nectar at asters and goldenrod, and a few late sulphurs, cabbage whites, and fritillaries linger. The mourning cloaks and commas that will overwinter as adults feed up now to survive the cold. Late asters and goldenrod are the key — leave them blooming to fuel the southbound monarchs through the month.
Trees This Month
September begins Maine's celebrated fall color, which sweeps south and downhill from the Canadian border through the month. The North Woods and western mountains turn first: the sugar maples flame orange and red, the red maples deepen to scarlet, the paper and yellow birches and the quaking aspens turn clear gold, and the understory striped maple and mountain ash add yellow and orange. By late month the interior is approaching peak.
The conifers stay green — the spruces, firs, and white pine that make up the Acadian forest hold their color and shed only old inner needles. The wild lowbush blueberry barrens turn brilliant red. Down East and on the coast the color lags a week or two behind the interior. The trees are pulling their chlorophyll back into the wood and dropping the first leaves; the great spectacle of the Maine autumn is fully underway, drawing leaf-peepers to Baxter, the Rangeley lakes, and the western hills.
Weather & Daylight
Across Maine, a typical September day averages a high near 68°F and a low near 46°F, with about 3.7 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Summer loosens its grip, high-60s afternoons and cooler mid-40s nights signal the turn toward fall.
| Average high | 68°F |
|---|---|
| Average low | 46°F |
| Precipitation | 3.7 in |
| Sunrise (mid-month) | 6:16 ET |
| Sunset (mid-month) | 18:50 ET |
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 (ET).
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One short note when Maine's next month turns — what's arriving, blooming, and worth a night outside.
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Same month elsewhere: September in Maryland · September in Massachusetts · September in Michigan