California Nature Guide: September 2026
Data updated: August 2026Sources & method · Corrections
September is one of California's warmest, driest months and the start of fall migration's crescendo. The hills stay golden, fire-watch peaks, and the high Sierra turns its first gold while the harvest — grapes, nuts, and the last stone fruit — fills the valley and the markets.
Week by week in September
September 3–9
- The Marin Headlands hawkwatch above the Golden Gate streams thousands of migrating raptors on a good September day.
- This is the great fall-planting month — set out brassicas and sow carrots, beets, lettuce, spinach, and peas.
- The wine-grape crush is on across Napa, Sonoma, the Central Coast, and Lodi; table grapes are at their sweet peak.
- The oaks are heavy with ripening acorns, the mast that feeds woodpeckers, jays, deer, and bears.
September 10–16
- Sparrow migration floods in — white-crowned, golden-crowned, fox, and Lincoln's sparrows fill the brush.
- The summer Milky Way still arches grandly while the Great Square of Pegasus and the Andromeda Galaxy rise in the east.
- Early apples, Asian pears, pomegranates, and the first persimmons mark the turn toward fall.
- The scarlet California fuchsia blazes on through the chaparral, the last great flower of the dry season.
September 17–23
- The autumn equinox around September 22 balances day and night as the nights begin to lengthen toward winter.
- Monterey Bay pelagic trips find shearwaters, storm-petrels, jaegers, and albatross at their fall best.
- The eastern Sierra aspens begin turning gold, the first wave of the West's great autumn color display.
- Pomegranates and persimmons (crisp Fuyu and soft Hachiya) come into full season.
September 24–30
- The first big flocks of snow and white-fronted geese trickle back into the Central Valley wetlands.
- Plant California natives, trees, and shrubs ahead of the coming rains so they establish on winter moisture.
- The nut harvest rolls on with walnuts and pistachios as the last summer fruit lingers.
- Monarchs begin gathering at the coastal overwintering groves, opening the great western monarch season.
Birds This Month
September is a peak of fall migration in California, and the variety is spectacular. Songbird migration crescendos: warblers (Townsend's, yellow, Wilson's, black-throated gray, and more), western tanagers, flycatchers, vireos, warbling vireos, and grosbeaks pour south through the riparian corridors and coastal points, and the famous vagrant season is on — California's coastal headlands and desert oases are legendary now for turning up eastern strays among the western migrants.
The shorebird migration continues at full strength on the Bay mudflats, the salt ponds, and the Salton Sea, with adults and now juveniles in fresh plumage. Raptor migration builds — the Marin Headlands hawkwatch above the Golden Gate is one of the West's premier hawk-migration sites, with thousands of red-tailed, sharp-shinned, and Cooper's hawks, turkey vultures, and the chance of a rarity streaming past on a good September day.
Offshore, Monterey Bay is at its pelagic best — shearwaters, storm-petrels, jaegers, Sabine's gulls, and albatross on a boat trip — and the first returning waterfowl trickle into the valley wetlands by month's end.
This month's tip: spend a clear September morning at the Marin Headlands hawkwatch or a coastal migrant point — the combination of streaming raptors, pouring songbirds, and the ever-present chance of a vagrant makes September one of the most thrilling months in California birding.
What's Blooming
September is the dry-season finale for California's wildflowers, with the lowlands at their most golden and parched and only the toughest late natives still in flower. The scarlet California fuchsia blazes on through the chaparral and dry slopes, a beacon for hummingbirds, and the late tarweeds (whose resinous scent defines the smell of California's golden hills), vinegar weed, California goldenrod, and gumplant hold on in the dry grasslands and along roadsides.
In the Bay and coastal marshes, the salt-marsh plants color the wetlands — the lavender of sea-lavender, the red of pickleweed turning with the season, and late gumplant. In the high Sierra, the flowering season is over, but the meadow grasses and the quaking aspens are beginning to turn. Watch, too, for the first response to any early rain: a few opportunistic natives can flush green at the very end of the dry season.
Where to see it: the dry-slope natives are the last flowers standing — seek the scarlet California fuchsia in the chaparral and the goldenrod and tarweed of the golden grasslands. The coastal fog belt and the salt-marsh edges of San Francisco Bay hold the most color. This is a month to appreciate the spare beauty of the dry season rather than a great bloom.
Garden This Month
September is the great fall-planting month across most of California, the cool-season counterpart to spring. As the worst heat begins to ease, set out transplants of broccoli, cabbage, cauliflower, kale, and chard and direct-sow carrots, beets, radishes, lettuce, spinach, peas, and cilantro — these cool-season crops will grow through the mild fall and produce all winter long in California's gentle climate, the foundation of the state's enviable year-round vegetable garden.
Keep harvesting the last of the summer crops — tomatoes, peppers, squash, and beans hold on into the warm September days — and pull plants as they finish, refreshing the soil with compost for the fall planting. Water the new seedlings through the lingering late-summer heat until the weather truly cools. September is also the time to plant cool-season flowers and California native plants in the warmer zones to be ready for the coming rains, and to plant garlic and onions for next year. In the Sierra and high foothills, harvest ahead of the first frost and begin the season's wind-down.
Zone 10a (mild coast, Los Angeles basin): excellent fall-planting weather on the coast — sow all the cool-season crops now for a long winter harvest, and set out brassica transplants. Keep the last summer crops going as the days shorten, and plant cool-season flowers as the marine layer cools the afternoons.
Zone 7a (Sierra foothills, higher inland): the season is winding down at elevation — sow fast cool-season crops (lettuce, spinach, radishes, garlic) and plant garlic for next year. Watch for the first fall frost, harvest tender crops before it arrives, and begin mulching beds for winter.
Zone 9b (Central Valley, inland Southern California): as the worst heat eases, this is the prime month to plant the fall and winter garden — set out broccoli, cabbage, cauliflower, and lettuce, and direct-sow carrots, beets, radishes, spinach, and peas. Keep harvesting the last summer crops, and water the new seedlings through the lingering September heat.
What's at the Farmers Market
September is harvest month in California, the markets straddling summer's end and the first taste of fall. The wine-grape crush is on across Napa, Sonoma, the Central Coast, and Lodi, and table grapes from the San Joaquin Valley are at their sweet peak. The nut harvest begins — the first almonds, walnuts, and pistachios from the Central Valley — and the late peaches, nectarines, and plums finish their long season.
The first fruits of fall arrive: early apples and Asian pears from the cooler districts, pomegranates beginning, the last figs, and the first persimmons late in the month. The summer vegetables hold on — tomatoes, peppers, eggplant, corn, and melons — joined by the first winter squash and pumpkins.
For selection and storage: choose grapes plump and firmly attached to green, pliable stems and refrigerate them unwashed; pick apples firm and store them cold; buy nuts in the shell and refrigerate or freeze shelled nuts to protect the oils. September is a wonderful market month — the overlap of the last summer fruit, the new grapes, the nut harvest, and the first apples gives the widest choice of the whole California year.
Night Sky This Month
September brings warm, settled, often crystal-clear nights to California and the autumn equinox around September 22, when day and night balance and the nights begin to lengthen toward winter. The dark-sky destinations remain excellent before the winter storms: the high Sierra (Yosemite, Sequoia and Kings Canyon, the Bristlecone Pine Forest), Lassen, and the deserts as their nights cool toward comfortable. Astronomy clubs hold some of their best public star parties in the steady September air.
The summer Milky Way still arches grandly overhead in early evening — the bright Sagittarius core sinking into the southwest while the Summer Triangle of Vega, Deneb, and Altair rides high. In the east, the autumn sky rises: the Great Square of Pegasus climbs, leading the chained constellations of Andromeda and Cassiopeia, and from a dark site you can find the faint smudge of the Andromeda Galaxy with the naked eye — one of the most distant objects visible without optical aid.
There is no major meteor shower in September. For this year's planet positions and the best moonless nights for the fading Milky Way, see the printable California night-sky guide.
Butterflies & Pollinators
September keeps California's butterflies active in the warm, dry late summer, with the year's most meaningful story building on the coast. The breeding monarchs of the final summer generation are maturing inland, and toward the end of the month the first of them begin drifting toward the Pacific Coast to start gathering at the overwintering groves — the opening of the great western monarch overwintering season that will peak in October and November.
The late-summer natives still feed a busy cast. The scarlet California fuchsia, the seed-setting buckwheats, goldenrod, and tarweeds draw hairstreaks, blues, metalmarks, painted ladies, gulf fritillaries, and fiery skippers, and the big western tiger swallowtail still patrols the watered streamsides and gardens.
To help them: as the monarchs begin moving toward the coast, keep native milkweed and late nectar available for the journey, but let the milkweed naturally die back rather than forcing late growth, which can disrupt the migration. Watered native nectar — California fuchsia, goldenrod, buckwheats, native sages, and zinnias — feeds all the late-season pollinators, and protecting the coastal overwintering groves is the single most important act for California's monarchs.
What to plant for them is in the California native plants guide
Trees This Month
September holds California's lowland trees at the end of the long dry season, the hills still golden and the oaks loaded with ripening acorns. The valley oaks, blue oaks, coast live oaks, and black oaks are heavy with their acorn crop now — the mast that feeds acorn woodpeckers, scrub-jays, deer, and bears, and that sustained California's native peoples for millennia. The California buckeye stands bare with its hanging pods, awaiting the rains to rouse it.
In the high Sierra, autumn arrives early. The quaking aspens of the eastern Sierra and the high basins begin turning gold, the first wave of the spectacular fall color that will sweep the range through October, and the mountain willows and cottonwoods start to color. On the coast, the coast redwoods and Pacific madrones hold their evergreen canopies, still drawing on the fog as the year's driest stretch hangs on before the first autumn rains finally break the long Mediterranean summer.
The California native plants guide covers what grows with them
Weather & Daylight
Across California, a typical September day averages a high near 85°F and a low near 56°F, with about 0.3 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Heat lingers into the mid-80s with nights near 56, rain still scarce, making it feel like summer refuses to loosen its grip.
| Average high | 85°F |
|---|---|
| Average low | 56°F |
| Precipitation | 0.3 in |
| Sunrise (mid-month) | 6:41 PT |
| Sunset (mid-month) | 19:08 PT |
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 (PT).
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Same month elsewhere: September in Colorado · September in Connecticut · September in Delaware