Run Lake Sonoma (Lake Sonoma 100K & 50K weekend)
Lake Sonoma 50 Mile
Geyserville/Healdsburg, CA (Lake Sonoma, South Lake Trailhead) → Lake Sonoma, CA (same trailhead)
Race guide
Updated 19 July 2026
The Lake Sonoma 50 Mile is a point-to-loop-and-back ultra set entirely within the rolling oak-and-chaparral terrain surrounding Lake Sonoma in Sonoma County, California, starting and finishing at the South Lake Trailhead near Geyserville/Healdsburg. Covering 80.5 km with 2,358 m of climbing, it is an out-and-back course that rewards honest, even-effort running rather than flashy climbing legs. The high point sits at just 353 m, so this is not an alpine race — but the relentless short, punchy climbs stacked throughout the day, combined with California spring heat, make it far more demanding than the elevation profile first suggests. With crew access at four aid stations and a hard 20:30 finish cut-off, it is a race that punishes poor pacing and rewards runners who treat the back half with serious respect.
Course & Terrain
The route follows the singletrack trails of Lake Sonoma Recreation Area, winding through sun-exposed chaparral, mixed oak woodland, and occasional riparian corridors as it traces the lake's shoreline ridges. The trail surface is generally well-maintained hardpack singletrack with rocky patches and rooted sections, but very little of it is flat — the course constantly rolls up and down short, steep ramps between drainages, giving runners very few long stretches to settle into a rhythm. From the South Lake Trailhead (70 m), you climb immediately to Island View at 7.2 km (248 m), then descend and undulate through to No Name Flat at 18.7 km (179 m) before climbing again toward Warm Springs Creek at 29.3 km (230 m). The final push to the Rancheria Creek turnaround at 40.6 km (346 m) is the highest point on the course, and the return leg simply reverses the entire route, meaning every climb you ran on the way out becomes a descent — and vice versa.
The Decisive Sections
The stretch from Warm Springs Creek to the Rancheria Creek turnaround (roughly km 29–41) is where the race is most often decided. It comes late enough in the first half that tired legs feel every extra meter of climbing, and the turnaround cut-off of 13:30 means there is a real time constraint to manage. Runners who go out too hard in the first 30 km frequently arrive at the turnaround with legs already compromised and face the brutal reality of the return leg. The return from Warm Springs Creek (km 51.9) back through No Name Flat (km 61.8) is the other make-or-break stretch — the No Name Flat cut-off of 17:00 gives a useful reality check, and anyone who has overcoooked the first half will feel the screws tightening here. The final 19 km from No Name Flat to the finish includes the re-climb through Island View (155 m at km 73.3) which, coming after 70+ km, feels much steeper than it did in the morning.
Pacing & Fueling Strategy
Because the course is an out-and-back with almost exactly mirrored climbing and descending, the classic approach is to run by feel and effort rather than pace — the short rolling terrain makes GPS pace unreliable and misleading. Target arriving at the Rancheria Creek turnaround (40.6 km) with at least 90 minutes to spare before the 13:30 cut-off; this gives you buffer without encouraging an unsustainably fast first half. Fuel early and consistently — aid station spacing ranges from roughly 7 to 12 km, which is manageable but not generous in the heat. Take on solid food and calories at No Name Flat and Warm Springs Creek on both the outbound and return legs, as these are also crew-accessible points where you can restock drops. Sodium management matters enormously given the potential for warm spring temperatures; plan your electrolyte intake proactively rather than reactively. Use crew access at South Lake Trailhead, No Name Flat, Warm Springs Creek, and the finish to pre-position exactly what you need for each segment rather than carrying excess weight across the full 80.5 km.
Conditions to Expect
Lake Sonoma runs in spring in Northern California's Sonoma County, a period when morning temperatures can start pleasantly cool but afternoons regularly climb into the mid-to-high 20s Celsius on exposed south-facing chaparral slopes. The terrain offers very little shade for long stretches, particularly on the ridge sections, and sun exposure combined with reflective dry grass makes the heat feel significantly more intense than ambient temperatures suggest. Wind is variable and can either offer relief or add to dehydration. Morning runners should carry a light layer for the pre-dawn or early-morning start but expect to strip it well before the turnaround. Dust is common on dry years; mud and slick roots can appear after wet winters. Check recent race reports for trail conditions specific to the year, but plan your kit and hydration strategy firmly around heat management as the default scenario.
Cut-offs & Crew Planning
The Lake Sonoma 50 Mile has three hard cut-offs you must respect: the Rancheria Creek turnaround at 13:30 (40.6 km), No Name Flat on the return at 17:00 (61.8 km), and the finish at the South Lake Trailhead at 20:30 (80.5 km). These cut-offs are tight enough to require consistent forward motion throughout the day — there is no room for a long sit-down crisis mid-race. Crew can access the course at South Lake Trailhead (start/finish), No Name Flat (both directions), and Warm Springs Creek (both directions), giving four meaningful intervention points each way. Communicate your expected arrival windows to your crew clearly, build in a buffer for heat-slowed sections, and have a clear plan for what you need at each stop to minimise time lost. Given the out-and-back format, your crew will leapfrog between just two or three road access points, so coordinate logistics in advance to avoid missed connections.
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Checkpoints & cut-offs
⚠ Auto-researched from public sources — aid stations and cut-offs may be incomplete. Confirm against the official roadbook before race day.
0 km · 70 m · —
6.9 km · 249 m · —
18.7 km · 179 m · —
27.2 km · 172 m · —
30.3 km · 214 m · —
40.6 km · 346 m · Sat 13:15
49.7 km · 193 m · —
52.8 km · 241 m · —
61.2 km · 175 m · Sat 16:45
73.2 km · 159 m · Sat 19:10
80.9 km · 70 m · Sat 20:30
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Course data researched from public sources — verify against the official roadbook.