August is harvest abundance and the late high-country bloom, when the Palisade peaches ripen on the Western Slope, the fall bird migration builds in earnest, and the alpine meadows shift toward autumn. The Perseid meteors streak the dark August skies, and hummingbirds and shorebirds stream south as the first hint of fall touches the highest peaks.
Week by week in August
July 30 – August 5
- Fall shorebird migration takes hold at the plains reservoirs and San Luis Valley wetlands as the mudflats dry.
- Rabbitbrush begins flushing gold along the foothill slopes, a great late-season nectar source.
- The legendary Palisade peaches arrive at their fragrant best from the Western Slope.
- Monarch numbers swell as the late-summer generation that will fly south is born on the showy milkweed.
August 6–12
- The Perseid meteor shower peaks around August 12 — the best of the year, often 50-plus an hour from a dark sky after midnight.
- Rocky Ford cantaloupe and watermelon hit their sweetest, and the first Pueblo green chiles arrive for roasting.
- Deep-blue fringed and Parry's gentians open in the high wet meadows, signaling the turning year.
- Common nighthawks gather into loose evening flocks over the towns on their way south.
August 13–19
- Swainson's hawks begin flocking toward their long migration to Argentina as rufous hummingbirds peak at feeders.
- The first gold flecks appear at the upper edges of the aspen belt in the coldest high basins.
- Tomatoes, eggplant, and the first winter squash flood the peak-season market tables.
- Direct-sow fall spinach, lettuce, and radishes and keep watering deeply through the late-summer heat.
August 20–26
- Returning sandpipers, yellowlegs, and dowitchers crowd the drying plains and San Luis Valley mudflats.
- Blooming rabbitbrush swarms with painted ladies, sulphurs, and skippers taking the late nectar.
- Rocky Mountain bee plant blooms purple-pink on the sandy ground as the prairie sunflowers peak.
- The summer Milky Way mirrors in Medano Creek at Great Sand Dunes on a clear, dark night.
August 27 – September 2
- The first sandhill cranes begin returning to stage in the San Luis Valley, building toward the October peak.
- Harvest the abundant summer crops for putting up — this is the heart of Colorado's preserving season.
- The southbound monarch passage begins, drifting down the South Platte and Arkansas corridors.
- Western Slope orchards reach their climax as the Palisade peaches come off the trees.
Birds This Month
August is when fall migration takes firm hold across Colorado. The plains reservoirs, playas, and the wetlands of the San Luis Valley fill with returning shorebirds — least, Baird's, and pectoral sandpipers, lesser yellowlegs, long-billed dowitchers, Wilson's phalaropes, and American avocets staging on the drying mudflats. Franklin's gulls and white-faced ibis gather, and the first southbound waterfowl appear.
The mountains are alive with movement. Southbound rufous hummingbirds swarm the foothill and montane feeders and the late wildflower meadows, fueling up alongside the resident broad-tailed hummingbirds, and mixed flocks of warblers, vireos, and flycatchers drift downslope and south through the foothill canyons. Band-tailed pigeons work the ripening Gambel oak acorns and chokecherries.
On the plains, common nighthawks gather into loose evening flocks over the towns, hawking insects on their way south, Swainson's hawks begin to flock toward their long migration to Argentina, and the grassland sparrows and the state bird lark bunting begin to drift. Lewis's woodpeckers and the year's young birds move through the foothills.
This month's tip: keep hummingbird feeders fresh and full through August for the migrating rufous hummingbirds — these fiercely territorial birds put on a spectacular show at feeders as they fuel up for the journey south.
What's Blooming
August carries Colorado's bloom into its late, golden phase, with the show now strongest in the late montane and subalpine meadows and on the plains. The high meadows blaze with fireweed, tall larkspur and monkshood, arrowleaf ragwort, asters, and the first gentians — including the deep-blue fringed and Parry's gentians that signal the turning year. The last Rocky Mountain columbine linger in the shaded high openings, and the alpine tundra fades from flower toward its autumn russet.
On the plains and foothills, the late-summer prairie comes into its own — golden sweeps of prairie sunflower, blanketflower, Maximilian sunflower, blazing star, gayfeather, and the first rabbitbrush beginning to gold. Rocky Mountain bee plant blooms purple-pink on the sandy ground, and the sandsage prairie around the Great Sand Dunes flowers. The roadsides and ditch banks of the Front Range fill with sunflowers and asters as the season tilts toward fall.
Garden This Month
August is the great harvest month in the Colorado garden and the moment the fall garden must go in. The summer crops pour in — tomatoes, peppers, squash, cucumbers, beans, and corn — and consistent deep watering and steady picking keep them producing through the late-summer heat. This is Colorado's peak preserving season, so plan to put up the surplus as it comes.
At the same time, the cool-season fall window opens along the Front Range. Direct-sow fall spinach, lettuce, arugula, radishes, beets, and carrots, and set out fall broccoli, cabbage, and kale transplants early in the month so they establish before the shortening days and cooling nights — Colorado's bright fall produces excellent cool-season crops. Keep new seedlings shaded and moist in the August sun. In the mountains, the calendar runs the opposite way: the first fall frost can arrive late this month at altitude, so keep frost cloth ready every night and harvest tomatoes and tender crops ahead of the freeze.
Zone 4b (mountain towns and high foothills): the short season is already winding toward its close — the first fall frost can arrive late this month at altitude. Harvest hard, keep frost cloth ready every night now, and pick or protect tomatoes and tender crops ahead of the first freeze. Sow only the very fastest greens for a possible last cutting.
Zone 5b (Front Range cities — Denver, Boulder, Fort Collins, Colorado Springs): peak harvest continues and the fall garden goes in. Keep watering and harvesting the summer crops, and direct-sow fall spinach, lettuce, radishes, beets, and carrots, plus set out fall brassica transplants early in the month so they size up before the cool nights. Keep hail cover handy.
Zone 6a (warmest Front Range and lower Western Slope — Grand Junction area): the long season allows a full fall planting. Keep the summer harvest going under consistent irrigation, sow fall and overwintering crops, and start cool-season greens that will run into late autumn in the mild Grand Valley. Stay ahead of grasshoppers and keep water steady through the late-summer heat.
What's at the Farmers Market
August is the peak of the Colorado market year, and the tables groan with the state's most famous crops. The legendary Palisade peaches from the Western Slope are at their fragrant best, the Rocky Ford cantaloupe and watermelons of the Arkansas Valley hit their sweetest, the Olathe sweet corn is in full swing, and the first Pueblo green chiles arrive, roasted by the bushel at the stands.
The summer harvest is at flood stage — tomatoes of every kind, peppers, eggplant, summer squash, cucumbers, green beans, onions, garlic, carrots, beets, the first winter squash, and abundant fresh herbs and sunflower bouquets. Colorado pantry staples continue: local honey, eggs, grass-fed beef, bison, and lamb.
For selection and storage: choose fragrant peaches that yield slightly and ripen firm ones on the counter, never the refrigerator; pick heavy melons with a sweet stem-end aroma; choose firm, glossy chiles and freeze roasted ones whole in their skins; and store tomatoes stem-side down at room temperature. This is the month to buy in bulk for canning, freezing, and chile-roasting.
Night Sky This Month
August is one of the finest stargazing months of the Colorado year, with warm nights, the blazing summer Milky Way, and the best meteor shower of the year all on offer. Head for the certified dark-sky destinations — Great Sand Dunes National Park, where the Milky Way mirrors in Medano Creek; the dark-sky town of Westcliffe-Silver Cliff and its Smokey Jack Observatory; Black Canyon of the Gunnison; Dinosaur National Monument; and Jackson Lake State Park on the plains. Many host their biggest star parties of the year this month.
The marquee event is the Perseid meteor shower, peaking around August 12 — the most popular shower of the year, often producing fifty or more meteors an hour from a dark sky after midnight, radiating from the northeast near Perseus. Overhead, the Summer Triangle stands high, the Milky Way pours down through Cygnus to the rich star clouds of Sagittarius and Scorpius in the south, and Antares glows red. This is prime deep-sky season for telescopes sweeping the summer nebulae and clusters.
Because moonlight and planet positions change each year and affect the Perseid view, check the printable Colorado night-sky guide for this year's specific viewing nights and planet visibility from your latitude. Pick a clear night between monsoon systems, find a dark horizon, and settle in after midnight for the meteor peak.
Butterflies & Pollinators
August keeps Colorado's butterfly numbers high, though the season is now tilting toward fall. The state insect, the Colorado hairstreak, still flies in the foothill and mesa Gambel oak scrub early in the month before fading. The late-summer meadows of the foothills and montane zone stay busy with fritillaries, checkerspots, blues, painted ladies, and a peak diversity of skippers nectaring on the asters, gentians, and rabbitbrush.
The high-country fliers are in their last weeks — the Rocky Mountain parnassian and the alpine fritillaries and arctics work the fading tundra flowers before the first frosts shut the high meadows down. On the plains, the monarch reaches its annual peak as the late-summer generation that will fly south is born on the showy milkweed of the river corridors, and painted ladies, orange and clouded sulphurs, and variegated fritillaries swarm the prairie sunflowers and rabbitbrush. Letting native milkweed and late-blooming asters and rabbitbrush stand now fuels both the resident butterflies and the southbound monarchs gathering for their long journey.
What to plant for them is in the Colorado native plants guide
Trees This Month
August holds Colorado's trees in late, full leaf, but the first whispers of autumn touch the highest elevations. The quaking aspen stand deep green across the slopes, though by late month the very first gold flecks appear in the coldest high basins and at the upper edges of the aspen belt, the leading edge of the great September turning. The dark conifers — Colorado blue spruce, Engelmann spruce, subalpine fir, and the high bristlecone pines — finish their short season of growth.
Down low, the Western Slope orchards reach their climax as the Palisade peaches ripen and come off the trees in the Grand Valley heat, the foothill Gambel oak acorns swell and begin to draw band-tailed pigeons and deer, and the chokecherries and serviceberries ripen their fruit for the birds and bears. The plains cottonwoods hold their summer green along the rivers, and the rabbitbrush on the foothill slopes begins to flush gold, an early signal that the Colorado fall is gathering at the top of the mountains and will soon roll downhill.
The Colorado native plants guide covers what grows with them
Weather & Daylight
Across Colorado, a typical August day averages a high near 81°F and a low near 52°F, with about 2.1 inches of precipitation — statewide averages from the 1991–2020 U.S. climate normals.
Still sultry and humid, highs lingering near 81F and warm nights in the low 50s under regular rainfall.
| Average high | 81°F |
|---|---|
| Average low | 52°F |
| Precipitation | 2.1 in |
| Sunrise (mid-month) | 6:14 MT |
| Sunset (mid-month) | 19:58 MT |
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 (MT).
Next month's version of this page, by email
One short note when Colorado's next month turns — what's arriving, blooming, and worth a night outside.
Go deeper with the Colorado guides
The complete Colorado birding, native-plant, and night-sky references — or the whole year, week by week, in one book.
Same month elsewhere: August in Connecticut · August in Delaware · August in Washington, D.C.