Arizona Nature Guide: September 2026
September winds down the monsoon and turns the high country to its first gold. Fall migration peaks, the desert heat begins to ease, and the aspens above Flagstaff start to color. It is a month of transition across every elevation.
What to look for this week
- Thousands of sandhill cranes roost and fly out at Whitewater Draw in the Sulphur Springs Valley, the height of Arizona's winter crane spectacle.
- Yuma winter lettuce and Salt River Valley grapefruit and Arizona Sweet oranges are at their national peak.
- The Quadrantid meteor shower peaks around January 3 in a brief, sharp burst, best after midnight from a dark desert site.
- The low-desert cool-season garden thrives — harvest lettuce, broccoli, and greens while the rest of the country freezes.
Birds This Month
September is a peak migration month in Arizona. Fall hawk migration is spectacular at the Grand Canyon's Yaki Point HawkWatch and over the southeastern mountains, where thousands of Swainson's, Broad-winged, and Cooper's Hawks, Turkey Vultures, and falcons stream south. The riparian corridors and desert oases fill with southbound migrant warblers, vireos, flycatchers, tanagers, and orioles, and the southeastern sky-island feeders still hum with late Rufous and other migrant hummingbirds before the first leave.
Shorebird migration continues at desert ponds and the Salt and Colorado rivers, and waterfowl begin returning to the wetlands. In the desert, the resident Cactus Wrens, Curve-billed Thrashers, Gambel's Quail, and Gila Woodpeckers stay active in the easing heat, and Phainopepla return to the lowland mesquite as the desert cools.
The grasslands of the southeast still hold their summer sparrows, and the first wintering raptors begin to filter back. The high country's breeding warblers and tanagers pull south, leaving the resident Mountain Chickadees, nuthatches, and jays in the cooling pine forests.
This month's tip: spend a morning at a hawkwatch — the Grand Canyon's Yaki Point or a southeastern ridge — to see the September raptor river, then bird a desert oasis for the wave of southbound songbirds.
What's Blooming
September carries the monsoon bloom into its final, golden flush. The desert floor still spreads with Arizona poppy, summer sunflowers, devil's claw, and spiderling, but the dominant note now is yellow composites — desert broom, seepwillow, burrobush, and roadside sunflowers bloom in masses that swarm with butterflies and bees. The barrel cacti finish their crown of orange flowers, and chuparosa and fairyduster may rebloom in the cooling weather.
The high country's wildflower season peaks and begins to fade into fall color. The Mogollon Rim and the San Francisco Peaks meadows blaze with late asters, goldenrod, gentians, and golden composites, and the first frosts at elevation begin to close the show. The aspen understory turns as the leaves above start to gild.
Where to look: the desert washes and roadsides around Phoenix and Tucson are gold with blooming desert broom and seepwillow — watch the butterflies swarming them. In the high country, the last asters and goldenrod color the meadows as the aspens begin to turn above them.
Garden This Month
September reopens the low-desert garden as the heat finally breaks. This is one of the two best planting months of the desert year: set out cool-season transplants — broccoli, cauliflower, cabbage, kale, chard — and direct-sow lettuce, spinach, carrots, beets, peas, radishes, turnips, cilantro, and other greens for the rich winter garden ahead, which will produce straight through the mild desert winter. Keep the fall tomatoes and peppers watered and fed as they begin setting fruit in the cooling weather, and continue harvesting summer crops.
Give citrus a deep watering and its final feeding of the year. The monsoon winds down, so resume more regular irrigation as the rains taper. In the transitional country, fall planting begins as the nights cool. In the high country, by sharp contrast, September brings the first frost — Flagstaff gardeners are harvesting the last tomatoes and squash ahead of the cold and putting beds to rest. The desert garden is waking just as the mountains close down for winter.
Zone 6b (Flagstaff and the high country): the season is ending — the first frost typically arrives this month, so harvest tender crops promptly and protect what you can. Sow quick fall greens under cover, and begin putting the high-country garden to bed for the long winter.
Zone 8b (higher desert, foothills, Tucson's edges): begin the fall cool-season garden too — sow greens, root crops, and peas, and set out brassica transplants as nights cool. The slightly cooler nights here give a comfortable head start on the winter garden.
Zone 9b (Phoenix, Tucson, lower valleys): the great fall planting month — as the heat eases, set out cool-season transplants (broccoli, cauliflower, cabbage, kale, chard, lettuce) and direct-sow carrots, beets, peas, radishes, spinach, and greens for the productive winter garden. Keep fall tomatoes and peppers watered as they set fruit in the milder weather.
What's at the Farmers Market
September markets span the harvest across Arizona's elevations. The desert and valley fields still bring melons, tomatoes, summer squash, eggplant, okra, and the late green chile harvest, now joined by autumn's winter squash — butternut, acorn, and spaghetti — and pumpkins. The first Medjool dates of the new harvest arrive from the Yuma and Salt River date gardens, plump and glossy.
The high country adds its short-season bounty: Verde Valley and Flagstaff-area apples, sweet corn, greens, and squash. Choose winter squash that feels heavy with a hard, dull rind and an intact stem; pick firm apples and fragrant melons. Winter squash and pumpkins store for months in a cool, dry place.
For selection and storage: this is prime date season — choose plump, glossy Medjools and store them airtight, refrigerated or frozen, for months. Cure winter squash in a warm spot for a week to harden the skin, then store cool and dry, and refrigerate the last summer vegetables to use promptly.
Night Sky This Month
September is one of the best stargazing months in Arizona — the monsoon fades, the air dries and steadies, and the nights turn comfortably cool under some of the darkest skies in the country. Flagstaff and Lowell Observatory, the Grand Canyon, the Mogollon Rim, and southern sites like Kitt Peak and Oracle State Park all offer superb transparent skies, and clubs resume fall star parties as the nights cool. The retreating monsoon leaves crisp, clear conditions ideal for deep-sky observing.
The sky is in its summer-to-autumn transition. The summer Milky Way still arches overhead in the early evening through Cygnus and down to Sagittarius, while the autumn constellations rise in the east — the Great Square of Pegasus, the chained princess Andromeda, and the Andromeda Galaxy (M31), the most distant object easily visible to the naked eye, climbing into prime view. The Summer Triangle rides high overhead.
The autumn equinox brings balanced days and nights and lengthening dark hours. September has no major meteor shower, but its clear, steady, moonless nights are excellent for galaxy hunting. For this year's exact planet positions and the best dark nights, see the printable Arizona night-sky guide.
Butterflies & Pollinators
September keeps Arizona's butterflies abundant as the monsoon bloom peaks in the desert washes. The masses of blooming desert broom, seepwillow, and roadside sunflowers swarm with Queens — the desert's signature milkweed butterfly, often gathering in spectacular numbers now — along with migrating monarchs moving south through the state. Two-tailed and Pipevine Swallowtails, Gulf Fritillaries, and clouds of sulphurs and whites work the late-summer flowers.
The southeastern canyons and grasslands hold their rich diversity a little longer — Bordered Patch, Arizona Sister, checkerspots, metalmarks, and a wealth of skippers and hairstreaks persist into the fall, and Mexican strays may still appear. The American Snout can erupt in great numbers after good rains, streaming across the southeast.
To help them: the blooming desert broom and seepwillow are a vital fall nectar source — leave them standing for the queens and monarchs fueling their southward movement. Keep garden lantana, milkweed, and zinnia going, plant native milkweed for the migrating monarchs and queens, and avoid spraying while butterflies are still abundant.
Trees This Month
September begins the turn in Arizona's high country. The quaking aspens on the San Francisco Peaks and the Mogollon Rim flush their first gold, and by month's end the highest groves around Flagstaff blaze yellow — the start of one of the West's great fall-color displays. The bigtooth maples in the sky-island canyons begin to turn red, and the Gambel oaks bronze. The ponderosa pines hold their green, scenting the cooling air.
In the desert, the trees feel the easing heat. The saguaro stands plump with its summer water, the palo verde and mesquite hold full canopies as the monsoon fades, and desert willow finishes blooming and sets long seed pods. The riparian cottonwoods along the rivers are still green but beginning, very slowly, to think of fall. Across the state, September is the hinge month — the desert green and easing toward its long mild autumn, while the mountains ignite with the first fire of fall color.
Go deeper with the Arizona guides
The complete Arizona birding, native-plant, wildflower, and night-sky guides — or the whole year in one bundle.
Same month elsewhere: September in Arkansas · September in California · September in Colorado