Missouri Nature Guide: September 2026
Data updated: August 2026Sources & method · Corrections
September eases Missouri into autumn — the great southbound monarch migration funnels through, fall warblers and raptors stream past, and the prairies turn to a sea of goldenrod and asters. The garden shifts to its fall crops as the heat finally breaks.
Week by week in September
September 3–9
- Broad-winged hawks migrate in swirling kettles on warm, sunny afternoons with light winds.
- Goldenrods reach full bloom against the deep purple of New England aster across the prairies and fields.
- Apples come into full season at the orchards alongside winter squash, pumpkins, and the last melons.
- The great monarch migration funnels south through Missouri, fueling on goldenrod, asters, and blazing star.
September 10–16
- Chimney swifts mass into huge tornado-like flocks that funnel into roost chimneys at dusk before departing.
- Prairie grasses flush copper and gold as big bluestem and Indian grass put on a show to rival the flowers.
- Plant garlic for next summer and sow cover crops on cleared beds to build and protect the soil.
- Monarchs cluster in trees at dusk to roost as the southbound flight peaks across the state.
September 17–23
- Sparrow migration begins as white-throated sparrows and the first dark-eyed juncos arrive for the winter.
- The autumn equinox falls around September 22; the Great Square of Pegasus rises in the east after dark.
- Black gum flares scarlet and sassafras turns orange, red, and gold as the first real fall color builds.
- Grape harvest peaks in the Hermann and Augusta wine country along the river bluffs.
September 24–30
- The last ruby-throated hummingbirds pass through as wintering yellow-rumped warblers and kinglets arrive.
- New England asters and the last goldenrods color the prairies, alive with the final migrating monarchs.
- Acorns rain down in a heavy mast year and pawpaws reach their soft, ripe peak in the bottomland woods.
- Watch the forecast in the north for the first frost; be ready to cover tender crops or harvest the last tomatoes.
Birds This Month
September is a major fall migration month in Missouri. The southbound warblers reach their peak, moving through the treetops in mixed flocks — though now in their subtler fall plumage, the famous 'confusing fall warblers.' River-bottom forests and wooded edges fill with American redstarts, magnolia, Tennessee, and bay-breasted warblers, alongside red-eyed vireos, rose-breasted grosbeaks, and scarlet and summer tanagers fattening for their journey.
The ruby-throated hummingbirds stream south, the last of the year passing through gardens and feeders in the first half of the month before nearly all depart. Overhead, broad-winged hawks migrate in swirling 'kettles' on warm, sunny days, and the common nighthawks finish their dramatic evening flights early in the month. Chimney swifts mass into huge tornado-like flocks that funnel into roost chimneys at dusk before departing.
The shorebirds continue south through the wetlands, and the first wave of returning waterfowl, sparrows, and yellow-rumped warblers hints at the winter ahead. Eastern bluebirds form loose post-breeding flocks, and the blue jays begin their conspicuous fall movements, caching acorns by the thousands.
This month's tip: watch for hawk kettles on warm September afternoons with light winds — broad-winged hawks ride the thermals in spectacular spiraling flocks. And catch the chimney swift roost spectacle at dusk, when thousands swirl into a single large chimney.
What's Blooming
September is the golden climax of Missouri's prairie and roadside year. The landscape turns to a sea of yellow and purple as the goldenrods reach full bloom — showy, stiff, and tall goldenrod blazing across the prairies and old fields — set against the deep purple of the New England aster and the soft blue and white of dozens of other asters.
The tall prairie flowers stand at their fullest: blazing star finishing its purple spikes, the towering sunflowers and compass plant, the deep purple ironweed, and the dusty-rose Joe-Pye weed in the swales. Sneezeweed and boneset bloom in the wet ground, and the prairie grasses themselves — big bluestem, Indian grass, and little bluestem — flush copper, russet, and gold, putting on a show as fine as any flower. The whole prairie hums with migrating monarchs working the late nectar.
Where to see it: the western prairies — Prairie State Park, Taberville, and Wah'Kon-Tah — are at their autumn peak, the goldenrod and asters alive with monarchs and the grasses glowing in the low light. Roadsides everywhere flush gold. Go in the warm afternoon to catch the monarchs and the prairie at its most luminous, or the cool morning for the freshest bloom.
Garden This Month
September is a welcome turning point in the Missouri garden as the brutal heat finally breaks and the fall crops come into their own. The cool-season vegetables planted in August — broccoli, cabbage, kale, lettuce, spinach, turnips, beets, and carrots — grow fast and sweet in the cooler days and nights, and many of these greens and roots actually improve with the first light frosts. Keep the warm-season crops going too, harvesting tomatoes, peppers, and beans until frost finally ends them.
Early in the month there is still time to direct-sow a final fast crop of spinach, lettuce, radishes, and arugula for autumn harvest. Toward month's end, begin the season's wind-down work: plant garlic for next summer's harvest, sow cover crops like winter rye or clover on cleared beds to protect and build the soil, and pull spent summer plants. In the northern counties, keep an eye on the forecast — the first frost can arrive late in September, so be ready to cover tender crops or harvest the last tomatoes.
Zone 5b (northern Missouri): the fall garden matures as the heat breaks. Harvest the cool-season greens, roots, and brassicas, and direct-sow a final quick crop of spinach, lettuce, and radishes early in the month. Plant garlic toward month's end, sow cover crops on empty beds, and watch for the first frost in the northern counties late in September.
Zone 6a (central Missouri): a productive transition month. Keep harvesting summer crops until frost while the fall greens and roots fill in, sow a last round of fast greens and radishes, and plant garlic and spring bulbs late in the month. Sow cover crops on cleared beds and begin cleaning up spent summer plantings.
Zone 6b (southern Ozarks and St. Louis area): the milder south extends the season. Plant fall greens, roots, and a final lettuce sowing, harvest the still-producing summer crops, and plant garlic late in the month. There is still time to establish cool-season crops and cover crops before the first frost, which usually holds off until October here.
What's at the Farmers Market
September markets in Missouri shift from summer abundance toward the bounty of the harvest season. The summer crops are finishing strong — the last of the tomatoes, peppers, okra, sweet corn, and melons — while the autumn fruits arrive in force. Apples come into full season at the orchards, and the first pears and the famous Missouri pawpaws appear, the latter ripening to a soft, custard-textured fruit.
The fall vegetables fill the tables: winter squash and pumpkins, sweet potatoes, broccoli, cabbage, kale, fall greens, beets, turnips, and carrots. This is grape harvest in the Hermann and Augusta wine country, and the first fall raspberries and storage onions and potatoes are in.
For selection and storage: choose apples that are firm with no soft spots and refrigerate them, where most varieties keep for weeks. Let pawpaws soften fully at room temperature before eating, as they ripen quickly and do not keep long. Cure and store winter squash and pumpkins in a cool, dry spot, and keep sweet potatoes in a warm, dark place rather than the refrigerator. Store the fall greens and roots cold and crisp in the crisper.
Night Sky This Month
September brings the autumn equinox around September 22, when day and night balance and the nights begin to lengthen noticeably, returning earlier darkness for stargazing. The sky is in transition — the Summer Triangle of Vega, Deneb, and Altair still rides high overhead in the evening, with the summer Milky Way arching through it, while the autumn constellations climb in the east.
The Great Square of Pegasus rises in the east, and below it the chain of stars leading to the Andromeda Galaxy — the most distant object visible to the naked eye, a faint smudge of light from two and a half million light-years away, lovely in binoculars from a dark sky. There is no major meteor shower at peak this month, so the early-evening Milky Way and the deep-sky objects of late summer and early autumn take the stage as the nights cool and clear.
The dark Ozark skies of Mark Twain National Forest are excellent now, with the comfortable temperatures and earlier darkness of September making for easy viewing, and the air often clearer behind autumn cold fronts. Because the planets and their positions shift each year, check the printable Missouri night-sky guide for this year's planet visibility and the best moonless viewing nights from your latitude.
Butterflies & Pollinators
September is the month of the great monarch migration in Missouri, the butterfly highlight of the entire year. The migratory generation pours south through the state, riding the cold fronts toward the overwintering forests of central Mexico, and on good days you can see dozens or hundreds streaming through, nectaring heavily on goldenrod, asters, and blazing star to fuel the journey. Watch for them clustering in trees at dusk to roost.
The migration is broad — alongside the monarchs, southbound clouds of clouded and orange sulphurs drift through, and painted ladies, red admirals, and common buckeyes move south as well. The prairies and gardens still hold great spangled fritillaries, fiery and other grass skippers, and the late broods of swallowtails, all working the abundant goldenrod and aster bloom.
To support them now: the September goldenrod and aster bloom is the single most important nectar resource for the migrating monarchs — every patch you leave standing fuels the journey south. Plant or preserve native goldenrods and asters, and resist mowing flowering roadsides and prairie patches this month. A garden full of late blooms can become a vital fueling station on the great central-flyway migration.
What to plant for them is in the Missouri native plants guide
Trees This Month
September brings the first real fall color to the Missouri forest, building toward the October peak. The earliest turners lead the way — the black gum (tupelo) flares brilliant scarlet, the sumacs and Virginia creeper turn deep red at the woodland edges, and the sassafras begins its mix of orange, red, and gold. The dogwoods, the state tree, deepen toward burgundy.
The autumn harvest of nuts and fruit begins in earnest. The hickories and black walnuts start dropping their nuts, the acorns rain down from the oaks in a heavy mast year, and the pawpaws reach their soft, ripe peak in the bottomland woods. The native persimmons begin to soften and drop after the first cool nights, finally losing their astringency. The cottonwoods and walnuts are among the first big trees to yellow and drop leaves, while the oaks, maples, and hickories hold their green a little longer, saving their color for October.
The Missouri native plants guide covers what grows with them
Weather & Daylight
Across Missouri, a typical September day averages a high near 80°F and a low near 57°F, with about 3.9 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Summer eases its grip as highs settle near 80 and nights cool into the upper 50s, feeling crisp by month's end.
| Average high | 80°F |
|---|---|
| Average low | 57°F |
| Precipitation | 3.9 in |
| Sunrise (mid-month) | 6:51 CT |
| Sunset (mid-month) | 19:19 CT |
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 (CT).
Next month's version of this page, by email
One short note when Missouri's next month turns — what's arriving, blooming, and worth a night outside.
Go deeper with the Missouri guides
The complete Missouri birding, native-plant, and night-sky references — or the whole year, week by week, in one book.
Same month elsewhere: September in Montana · September in Nebraska · September in Nevada