The Mount Flume via Osseo Trail is a 10.5-mile out-and-back with 3,122 ft of elevation gain.
10.5 mi • 3,122 ft gain • 5-9 hours • Lincoln Woods Trailhead
Feels like 40°F
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Upgrade to UnlockSummit-level conditions by time of day at 4,328' elevation
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Today Sep 22 | Tomorrow Sep 23 | Thursday Sep 24 | |||||||
|---|---|---|---|---|---|---|---|---|---|
| AM | PM | night | AM | PM | night | AM | PM | night | |
| Temperature & Wind | |||||||||
| Weather | cloudy | cloudy | clear | sunny | sunny | clear | sunny | sunny | clear |
| Temp °F hi / lo | 39° 37° | 42° 39° | 41° 39° | 40° 38° | 42° 39° | 43° 41° | 43° 41° | 48° 43° | 47° 45° |
| Chill °F | 33° | 33° | 30° | 29° | 31° | 33° | 34° | 41° | 42° |
| Wind mph | 5 | 8 | 18 | 17 | 14 | 14 | 12 | 4 | 6 |
| Gust mph est. | — | 12 | 29 | 27 | 22 | 22 | 19 | — | — |
| Precipitation | |||||||||
| Precip in (rain/snow) | - | - | - | - | - | - | - | - | - |
| Freezing ft | 9,443 ft | 10,530 ft | 11,600 ft | ||||||
| Conditions | |||||||||
| Cloud cover | 100% | 100% | 2% | 2% | 2% | - | - | - | - |
| Vis mi | 9 | clear | clear | clear | clear | clear | clear | clear | clear |
| UV | 4 | 6 | — | 4 | 5 | — | 4 | 5 | — |
Tap a day header to expand AM/PM/Night detail
| Elevation | Today Sep 22 | Tomorrow Sep 23 | Thursday Sep 24 |
|---|---|---|---|
| lo/hi °F · wind mph & dir · chill °F | |||
| Summit 4,328 ft | 37/39° 5 | 38/40° 17 | 41/43° 12 |
| 4,100 ft | 38/40° 5 | 39/41° 17 | 41/43° 12 |
| 3,300 ft | 41/43° 9 | 41/42° 17 | 43/46° 11 |
| 2,500 ft | 43/46° 9 | 43/45° 15 | 46/49° 8 |
| Trailhead 2,000 ft | 44/48° 7 | 44/47° 12 | 47/52° 6 |
4 more days of forecast — plan around the weather window, not just tomorrow.
Full hourly summit forecasts: Mount Flume weather
Follows the Lincoln Woods Trail and the Osseo Trail from the Kancamagus Highway, climbing a long ridge with a series of wooden staircases to the Franconia Ridge Trail and the summit's sharp, exposed ledges. The Flume Slide Trail is a steep, slabby alternative best avoided when wet.
Distance
10.5 mi
Elevation Gain
3,122 ft
Duration
5-9 hours
Trailhead
Lincoln Woods Trailhead
The Mount Flume via Osseo Trail is 10.5 miles round trip, starting at Lincoln Woods Trailhead. At AMC book time — half the distance in hours plus 30 minutes per 1,000 ft of climbing — that works out to roughly 5-9 hours. Most parties take longer than book time on rough or above-treeline terrain, in winter, or with a heavy pack.
The Mount Flume via Osseo Trail climbs about 3,122 ft over 10.5 miles — an average of roughly 296 ft of gain per mile. That figure is cumulative ascent across the whole out-and-back, not the difference between the trailhead and the high point.
HikerNerd rates the Mount Flume via Osseo Trail Difficult, scored with the Shenandoah difficulty formula — √(elevation gain × 2 × distance) — applied to its 10.5 miles and 3,122 ft of gain. The score measures physical effort only. Above-treeline exposure, water crossings, and winter conditions can make a moderate-rated route the hardest day of your year, so check current conditions before committing.
The Mount Flume via Osseo Trail summits 1 named peak: Mount Flume.
The Mount Flume via Osseo Trail starts at Lincoln Woods Trailhead. Check the trail alerts on this page before you drive — trailhead access and parking in the White Mountains change with closures and construction.
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