August is the peak of Iowa's harvest — sweet corn, tomatoes, and melons all at once — and the prairie shifts toward its late, gold-and-purple phase. Shorebird and early songbird migration build, the nights grow darker, and the first hint of autumn enters the morning air by month's end.
Week by week in August
July 30 – August 5
- The prairie shifts toward late summer — goldenrods begin, ironweed flares deep purple, and rough blazing star opens on the Loess Hills slopes.
- Common nighthawks gather into loose, swooping evening flocks — one of the surest signs of approaching fall.
- Sow the last fast fall crops — spinach, lettuce, radishes, and turnips — early in the month so they mature before frost.
August 6–12
- The Perseid meteor shower peaks around August 12, often producing dozens of meteors an hour after midnight from a dark Loess Hills site.
- The melons arrive in force — watermelon and muskmelon, including the famous sandbar-grown Muscatine melons from the Mississippi bottoms.
- The monarch buildup begins as the migratory 'super generation' matures and starts concentrating at the late prairie blooms.
August 13–19
- The market peaks — sweet corn at its height alongside tomatoes, peppers, melons, and the first winter squash all at once.
- Common buckeyes reach peak abundance and clouds of sulphurs work the fields as butterfly numbers stay high on the late prairie.
- Adult and young ruby-throated hummingbirds swarm feeders and flowers, fueling up for the long flight south.
August 20–26
- Goldenrod, tall ironweed, and Joe-Pye weed drench the late-summer prairie in gold and purple, alive with bees and migrating monarchs.
- Early-departing songbirds slip away as orioles, warblers, and flycatchers begin moving south through the timber.
- The first hints of fall appear — a few black walnuts and black gums begin to yellow and redden, and cottonwoods show scattered gold leaves.
August 27 – September 2
- Shorebird migration is in full swing on drawn-down wetlands, with sandpipers and yellowlegs staging across the state.
- Monarchs gather toward the end of August, the first act of the great fall migration about to funnel south through Iowa.
- Keep harvesting daily, pull spent plants, and sow a cover crop on cleared beds as the fall garden takes shape.
Birds This Month
August is the quiet turn toward fall migration in Iowa. Songbird song fades as breeding ends, but movement picks up: shorebird migration is in full swing on drawn-down wetlands and mudflats, with pectoral, least, and semipalmated sandpipers, lesser yellowlegs, and others staging across the state. Adult and young ruby-throated hummingbirds swarm feeders and flowers, fueling up for their long flight south, and common nighthawks gather into loose, swooping flocks at dusk — one of the surest signs of approaching fall.
Early-departing songbirds slip away — orioles, warblers, and flycatchers begin moving — and chimney swifts mass over town chimneys. Purple martins stage in large pre-migration roosts. On the prairie, dickcissels and goldfinches are still active, the goldfinches feeding their late-season broods on the seed-laden thistles and sunflowers.
This month's tip: keep hummingbird feeders clean and full through late August and into September — the southbound peak passes now, and your feeders may be a key fueling stop. Leaving them up does not delay migration.
What's Blooming
August shifts the Iowa prairie into its late-summer palette of gold and purple. The blazing stars (Liatris) peak, the compass plant and prairie dock tower in yellow bloom, and the prairie sunflowers and oxeye light up the grassland. The signature plants of late summer take over: drifts of goldenrods of many species, the tall ironweed in deep royal purple, Joe-Pye weed in the wet swales, and rough blazing star on the dry Loess Hills slopes.
The big bluestem and Indian grass reach their full towering height, their stems flushing with the first reds and golds. The earliest asters begin opening, hinting at the coming fall bloom. Roadsides and ditches glow with goldenrod, sunflowers, and the rose-purple of ironweed — the prairie at its richest, deepest color of the year, alive with bees, butterflies, and migrating monarchs.
Garden This Month
August is the height of the Iowa harvest and the busiest picking of the year. Tomatoes, peppers, sweet corn, beans, cucumbers, summer squash, melons, and the first winter squash and potatoes all come in at once. Pick daily, keep tomatoes evenly watered to prevent cracking and blossom-end rot, and stay ahead of the late-summer pests — squash bugs, hornworms, and stink bugs are all at their peak.
This is also the month to set up the fall garden in earnest. Sow the last fast crops — spinach, lettuce, arugula, radishes, turnips, and a final round of bush beans — early in the month so they mature before frost. Keep newly seeded fall beds moist in the heat, and as crops finish, pull spent plants and either replant or sow a cover crop. Begin planning garlic beds for an October planting, and keep harvesting and preserving as the abundance pours in.
Zone 4b (far north Iowa): harvest hard as the short season races toward its early frost — pick tomatoes, beans, and squash, and start watching the forecast late in the month, since the first light frost can arrive here as early as mid-September.
Zone 5a (central Iowa): the garden is at peak harvest; keep picking, water through any dry spell, and sow the last quick fall crops — spinach, lettuce, radishes, and turnips — early in the month for an autumn harvest.
Zone 5b (southern Iowa): the longest season — keep harvesting through the heat, sow fall greens and roots, and plant garlic-bed cover crops; tomatoes and peppers will keep producing well into autumn here.
What's at the Farmers Market
August is the fullest month at Iowa markets, when the whole summer harvest peaks at once. Sweet corn is at its height — the iconic Iowa crop is everywhere — alongside vine-ripe tomatoes in every color, peppers, cucumbers, green beans, summer squash, eggplant, potatoes, onions, and the first winter squash. The melons arrive in force: watermelon and muskmelon (cantaloupe), including the famous sandbar-grown Muscatine melons from the Mississippi River bottoms.
Peaches, blackberries, the first apples, and abundant cut flowers and honey round out the stands. Buy sweet corn the day you'll use it and keep it husked and cold. Store tomatoes and melons at room temperature for best flavor, choosing melons that smell sweet at the stem and yield slightly to pressure. Keep cucumbers and squash cool and use them while crisp.
Night Sky This Month
August brings the best-known meteor shower of the year to Iowa's skies and the summer Milky Way at its finest. The Perseid meteor shower peaks around August 12, often producing dozens of meteors an hour from a dark site after midnight — one of the most reliable and beloved sky events, best watched from a dark place like the Loess Hills, far from city lights. The summer nights are warm and finally lengthening again, making for comfortable late-evening viewing.
Overhead, the Summer Triangle rides high, and the Milky Way arches across the whole sky from Cassiopeia in the northeast down through Cygnus and Aquila to the rich star clouds of Sagittarius and Scorpius in the south. Binoculars sweep up countless clusters and star fields along that band on a clear, dark night.
Exact Perseid peak timing and planet positions shift year to year — the printable Iowa night-sky guide gives the current details for your location.
Butterflies & Pollinators
August keeps Iowa's butterfly numbers high and begins the great monarch buildup. The monarch generation maturing now includes the special migratory 'super generation' — long-lived, non-breeding adults that will fly all the way to central Mexico — and they begin concentrating at the late prairie blooms to fuel up. Blazing star, goldenrod, ironweed, and prairie sunflowers draw them, along with great spangled fritillaries, painted ladies, red admirals, and clouds of sulphurs.
Common buckeyes reach their peak now as the summer's southern migrants build to their largest numbers, their bold eyespots common in roadside ditches and prairies. Eastern tiger and black swallowtails fly their later broods, and the prairie skippers remain active. The late-blooming, nectar-rich prairie of August is one of the best butterfly habitats of the Iowa year — and watching monarchs gather toward the end of the month is the first act of the fall migration to come.
Trees This Month
August finds Iowa's trees in late, dust-darkened summer green, with the first hints of the turn ahead. The nut crops are filling fast: black walnuts hang heavy in their green husks, shagbark hickory and bitternut hickory nuts harden, and the bur oak and red oak acorns swell toward their fall drop. The catalpa seed pods lengthen into their long, slender 'cigars.'
By late August the earliest fall color appears in stressed or early-turning trees — a few black walnuts and black gums begin to yellow and redden, and drought-stressed trees in a dry year may drop leaves early. The cottonwoods show their first scattered yellow leaves along the rivers. The serious color is still weeks away, but the lengthening nights are already signaling the timber toward autumn.
Weather & Daylight
Across Iowa, a typical August day averages a high near 82°F and a low near 60°F, with about 4.1 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Still hot and humid, highs near 82 and sultry nights around 60, with thunderstorms remaining a regular afternoon fixture.
| Average high | 82°F |
|---|---|
| Average low | 60°F |
| Precipitation | 4.1 in |
| Sunrise (mid-month) | 6:21 CT |
| Sunset (mid-month) | 20:16 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: August in Kansas · August in Kentucky · August in Louisiana