Trail Log · Sunday, May 24, 2026
Kelly Flats
- OutUp Heart Attack Hill10.3 mi
- BackDown Aneurysm Hill10.8 mi
Out and back from Kelly Flats Campground
Poudre Canyon, Roosevelt National Forest, off CO 14 northwest of Fort Collins. Out and back from Kelly Flats Campground, on trail 8:55 to 11:53 AM in Sucia, a 2021 Jeep Wrangler JLU Sport.
Trail review
From our run, the track, and the published guides
The trail
Kelly Flats climbs out of Poudre Canyon from Kelly Flats Campground and runs west-northwest along a ridge with views of the Mummy Range. COTREX and FunTreks both rate it difficult and put it at about 10.5 miles one way, with a rocky first section and mud holes toward the far end. Half a mile in, the trail splits: Heart Attack Hill goes straight up, very steep and loose, and a loop to the east, Aneurysm Hill, goes around it over loose rock and tall boulders. Trails Offroad reviewers are split on which of the two is harder.
Our run
This was our third time on Kelly Flats, on the Sunday of Memorial Day weekend, and we took one of each: Heart Attack Hill on the way out and Aneurysm Hill on the way back. On the track, Heart Attack Hill holds the steepest pitch of the day, 31% over 100 m at 9:06 AM, and gains 565 ft in a mile. Aneurysm Hill came down as steep as 28% and dips to 6,881 ft before it rejoins the main trail. In between, the ridge ran 10.3 miles out to a turnaround at 10:20, and the high point, 8,653 ft, came just after it on the way back. Sucia was stopped only 12 minutes in three hours.
“Kelly Flats where you can choose between a heart attack or an aneurysm!”
Good to know
- At the half-mile split, Heart Attack Hill is the direct line and Aneurysm Hill is the loop to the east. The two rejoin about a mile up.
- FunTreks lists a May 15 opening and notes that a wet spring often delays it. We ran it May 24.
- COTREX warns that the trail gets extremely muddy after rain.
- The Chutes are optional; FunTreks says body damage is a frequent occurrence there.
Elevation
Feet along the track, from the USGS 10 m elevation model
- Heart Attack Hill
- Kelly Flats trail
- Aneurysm Hill
The day
8:55–11:53 AM · moving 2h 46m, stopped 12 min across 6 stops
- Heart Attack Hill
- Kelly Flats
- Aneurysm Hill
- Stopped
Leg by leg
| Leg | Road | Time | Distance | Moving | Stopped | Elevation |
|---|---|---|---|---|---|---|
| Up from the campground | Kelly Flats trail | 8:55–9:01 AM | 0.54 mi | 6 min | 0 | 6,793 → 7,048 ft |
| Heart Attack Hill | Main line, uphill | 9:01–9:16 AM | 1.03 mi | 15 min | 0 | 7,048 → 7,613 ft, 31% pitch |
| Out the ridge to the turnaround | Kelly Flats trail | 9:16–10:20 AM | 8.77 mi | 1h 02m | 2 min | 7,613 → 8,518 ft |
| Back along the ridge | Kelly Flats trail | 10:20–11:26 AM | 8.64 mi | 1h 02m | 5 min | high 8,653 ft |
| Aneurysm Hill | East loop, downhill | 11:26–11:43 AM | 1.71 mi | 16 min | 0 | 7,614 → 7,061 ft, low 6,881 ft |
| Down to the campground | Kelly Flats trail | 11:43–11:53 AM | 0.46 mi | 5 min | 5 min | 7,061 → 6,818 ft |
| Total | 8:55–11:53 AM | 21.2 mi | 2h 46m | 12 min | +4,300 ft |