September is when Texas turns the corner. The heat starts to break in the second half of the month, fall migration ramps into high gear, and the first cool front feels like the whole state exhaling. It is one of the most exciting months of the nature year.
Week by week in September
September 3–9
- Broad-winged hawks begin to stream south; kettles of thousands funnel through Texas toward the Coastal Bend in coming weeks.
- Goldenrod, frostweed, and fall asters open across the state, building the nectar buffet for migrating monarchs and queens.
- Plant fall greens, carrots, beets, and broccoli now; the cooling soil and shorter days favor cool-season crops again.
- The bright star Fomalhaut, the lonely star of autumn, climbs low in the southeast on early-September evenings.
September 10–16
- Hawk migration peaks; watch for huge kettles of broad-winged hawks riding thermals south over central and coastal Texas.
- Frostweed and mistflower swarm with butterflies, and Maximilian sunflowers begin their tall golden show along roadsides.
- Keep planting cool-season crops; ruby-red grapefruit and oranges in the Valley are sizing up toward winter ripeness.
- The Great Square of Pegasus rides high in the east in the evening, the unmistakable signpost of the autumn sky.
September 17–23
- The leading edge of the monarch migration enters Texas; raptors and songbirds continue pouring south on northerly winds.
- Maximilian sunflowers and frostweed peak as fall asters open, fueling the first big waves of southbound monarchs.
- Transplant fall broccoli, cabbage, and lettuce; the fall equinox around September 22 brings balanced day and night.
- The fall equinox falls around September 22, when day and night run nearly equal as the sun crosses the celestial equator.
September 24–30
- Fall migration is at full force; the first wintering sparrows and ducks arrive as broad-winged hawks finish passing through.
- Frostweed, mistflower, and goldenrod still draw clouds of monarchs and queens fueling up for the trip to Mexico.
- Sow spinach, lettuce, and radishes; pecans, the state tree, begin to fill out their shells toward an October harvest.
- Look for the Andromeda Galaxy as a faint smudge near Pegasus, the most distant object easily seen with the unaided eye.
Birds This Month
September is the big month for fall migration in Texas. Warblers pour through — American redstarts, black-and-white warblers, Nashville warblers, and many more drip through the coastal woodlots at High Island and Sabine Woods and the Hill Country motts, especially after a north wind drops them out of the sky. Vireos, orioles, and flycatchers move with them, and the coast can be electric on the right morning.
The signature September spectacle is the raptor flight. Broad-winged hawks funnel down through Texas by the tens and hundreds of thousands, riding thermals in swirling 'kettles' on their way to South America. The Hawk Watch at Smith Point on Galveston Bay and the Hazel Bazemore County Park count near Corpus Christi are the premier viewing sites, with single-day broad-wing counts that can run into the hundreds of thousands in late September.
Shorebirds keep moving through coastal and inland mudflats, and hummingbird numbers stay high at feeders as ruby-throated and rufous hummingbirds stream south — keep the nectar coming, since these birds need the fuel for a long journey. Late in the month, the very first wintering sparrows and ducks begin to trickle into the state.
This month's tip: watch the weather. The morning after a cold front, with north winds, is the single best time to be at a coastal migrant trap or a hawk-watch platform in September.
What's Blooming
September is the start of the great fall bloom, and the prairies turn gold and purple. Maximilian sunflower reaches its towering peak across the Hill Country and Blackland Prairie, and goldenrod lights up roadsides and old fields statewide. The much-maligned ragweed blooms now too — the inconspicuous green-flowered plant that is actually responsible for the fall allergy season that goldenrod gets blamed for.
This is also peak fall aster season, with native asters opening in clouds of pale lavender, and the all-important Gregg's mistflower and frostweed hitting their stride as nectar plants. These are the flowers that fuel the monarchs and queens beginning to funnel south through Texas now, and a roadside patch of mistflower can be alive with butterflies on a warm September afternoon.
Where to see it: any prairie remnant or untended field in the eastern two-thirds of the state will be gold with sunflower and goldenrod, and the LBJ Wildflower Center in Austin showcases the fall natives. Visit on a still, warm day to catch the pollinators at work.
Garden This Month
September is arguably the best vegetable-planting month of the entire Texas year. The soil is still warm enough for quick germination, but the air is finally cooling, and the cool-season crops you start now will produce through fall and winter. Set out transplants of broccoli, cabbage, cauliflower, kale, and collards, and direct-sow carrots, beets, radishes, turnips, lettuce, spinach, and chard.
Keep your fall tomatoes well watered and lightly fed so they set and ripen fruit before the first frost. Two habits matter most in early fall: keep seedbeds consistently moist until germination (the soil still dries fast in the September sun), and start scouting for cabbage loopers and other caterpillars that find tender new cole crops quickly. Mulch new plantings to hold moisture as the rains return, and this is also a fine time to divide and plant perennials and to over-seed cool-season color.
Zone 8a (north & north-central Texas): this is the prime fall planting month — set out broccoli, cabbage, cauliflower, and kale transplants and direct-sow carrots, beets, radishes, lettuce, and spinach. Keep fall tomatoes watered and fed so they set fruit before the first frost in November.
Zone 8b (central Texas): sow cool-season greens, root crops, and cole-crop transplants now while the soil is still warm enough for fast germination but the air is cooling. A great month for lettuce, spinach, chard, carrots, and broccoli.
Zone 9a (Gulf coast & south): begin the long fall-and-winter garden — transplant broccoli and cabbage, sow greens and root crops, and keep fall tomatoes and peppers producing into the mild autumn ahead.
Zone 9b (deep south Texas): the heat is easing — plant cool-season crops generously (greens, carrots, beets, cole crops) and continue with peppers and tomatoes that will produce through the warm South Texas fall.
What's at the Farmers Market
September markets bridge summer and fall. The last good watermelons and cantaloupes linger early in the month — choose melons heavy for their size with a deep, hollow thump. Okra keeps producing in the heat; pick the small, tender pods and use them within a few days before they toughen.
Fall pumpkins and winter squash begin arriving from the Panhandle fields. Choose winter squash and pumpkins with hard, unblemished rinds and an intact stem — they store for weeks to months in a cool, dry, well-ventilated spot, not the refrigerator. Sweet potatoes from the East Texas crop start to show; cure and store them warm and dry rather than cold, which makes them hard and off-flavored.
Late-summer tomatoes, peppers, and eggplant fill out the stalls, and the first cool-weather greens may appear at month's end. Shop early in September for the best of the melons and the first of the fall storage crops.
Night Sky This Month
September brings the autumnal equinox around September 22, when day and night are nearly equal and the nights begin to grow longer faster than at any other time of year — good news for stargazers, who no longer have to wait so late for full dark. The evenings are mild and the air often clearer after a passing front.
The summer sky still dominates early evening: the Summer Triangle of Vega, Deneb, and Altair rides high overhead, and the Milky Way arches from north to south through the heart of it, still showing its bright core low in the southwest after dark. As the night deepens, the great square of Pegasus climbs in the east, ushering in the autumn constellations and the faint smudge of the Andromeda Galaxy, visible to the naked eye from a dark site.
West Texas — the Big Bend region and the Davis Mountains around McDonald Observatory — offers the darkest skies in the state for this transition. Planet positions and the year's exact viewing details change annually; the printable Texas night-sky guide lists this year's specifics from your latitude.
Butterflies & Pollinators
September is one of the great butterfly months in Texas, defined by the start of the fall monarch migration. Late in the month, monarchs begin funneling south through the state on their way to the overwintering forests of central Mexico — a river of orange that will swell into October. They follow the central flyway, and a blooming patch of mistflower or frostweed can hold a remarkable concentration of them.
Queens, the monarch's russet look-alike, are abundant now and often outnumber the early monarchs, so look closely — queens lack the strong black wing veins of the monarch. Gulf fritillaries, sulphurs, and the swallowtails remain active, all crowding onto the fall nectar.
To bring them in: the key now is nectar, not host plants — a generous, blooming succession of Gregg's mistflower, frostweed, lantana, goldenrod, and zinnias will pull migrating monarchs and queens right into the yard. Native milkweed left standing also gives any late breeders a place to lay. A patch of damp sand offers drinking water during the warm afternoons.
Trees This Month
September is the first whisper of the change to come. Pecans, the state tree, are filling out their nuts toward the October-into-November harvest, and the husks will soon begin to split. The native cedar elm produces its unusual small fall bloom this month — most elms flower in spring, but cedar elm is one of the few that flowers in autumn — and will be among the earliest trees to color up.
Along the Hill Country rivers, bald cypress still wears soft green but stands weeks from the rusty-orange it will take on in November. In the Piney Woods of east Texas, the sweetgum and the first understory trees show a hint of early color where they are drought-stressed, a preview of the season's real display. Live oaks remain solidly green, holding their leaves as always until next spring's exchange.
Weather & Daylight
Across Texas, a typical September day averages a high near 88°F and a low near 64°F, with about 3.1 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Heat eases slightly into the upper 80s, nights cool toward 64, while rainfall surges back to summer-storm levels.
| Average high | 88°F |
|---|---|
| Average low | 64°F |
| Precipitation | 3.1 in |
| Sunrise (mid-month) | 7:15 CT |
| Sunset (mid-month) | 19:38 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).
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Same month elsewhere: September in Utah · September in Vermont · September in Virginia