Lake Sonoma 100K and 50K 2027 Guide: Course, Aid, Cutoffs and Cup Rules
Quick answer: Lake Sonoma runs on Saturday, April 10, 2027 at the Lake Sonoma Visitor Center near Healdsburg and Geyserville, California. There is no 50 mile race in 2027: the event is now a 100K (5:00 AM start, 15,000 feet of climbing, 19 hour limit, Western States qualifier), a 50K (7:30 AM, 5,700 feet, 11 hours) and the women's Trail Sisters Half Marathon (9:30 AM, 5 hours). Every distance is cupless and you must carry at least one bottle. The longest gap between aid is 6.9 miles, and pacers and trekking poles are not allowed.
Lake Sonoma 2027 at a glance
| Item | 100K | 50K | Trail Sisters Half |
|---|---|---|---|
| Date | Sat, April 10, 2027 | Sat, April 10, 2027 | Sat, April 10, 2027 |
| Start | 5:00 AM, Visitor Center | 7:30 AM, Visitor Center | 9:30 AM, Lone Rock |
| Distance | 62.1 miles (table) | 31.1 miles (table) | 13.1 miles |
| Climbing | 15,000 ft | 5,700 ft | 2,339 (race figure) |
| Time limit | 19 hours, midnight | 11 hours, 6:30 PM | 5 hours, 2:30 PM |
| Fee to Dec 31 | $280 | $185 | $110 |
| Fee from Jan 1 | $300 | $200 | $115 |
From the race's official website and UltraSignup page, read October 12, 2026. Fees are before processing fees and taxes, and the first tier ($250, $165, $95) ended October 12. Registration closes April 9 at 11:59 PM PT; no field cap or lottery is stated. The event is owned and run by Trail Sisters LLC, with race directors Gina Lucrezi and Justin Keller. The homepage meta text says April 11, but the race pages and UltraSignup say Saturday, April 10. Official pages differ on whether the 100K qualifies for Western States 2027 or 2028; the homepage and UltraSignup say 2028, with a finish under 19 hours.
The courses
The 100K starts with a climb up Pritchett Peak to a water only stop, comes back down toward the Visitor Center, then climbs to South Lake Trailhead for an out and back on the original Lake Sonoma course to Lone Rock before returning to the finish. The 50K is a loop that crosses the lake bridge, passing South Lake, Island View, Warm Springs, Wulfow, Liberty Glen and Bummer. The Half is point to point from Lone Rock Trailhead to the Visitor Center over "relentless rolling hills." 100K flagging is orange and Half flagging is pink.
Aid stations and the gaps between them
The 100K has 8 full aid stations and 5 water only stops. Full stations carry Skratch Hydration Mix and Skratch Chews plus savory and sweet food. Mileages are approximate.
| Mile | 100K aid station | Type | Miles to next | Cutoff | Crew / drop bag |
|---|---|---|---|---|---|
| 5.8 | Pritchett Peak | Water only | 5.6 | ||
| 11.4 | Woodridge | Full | 1.3 | Drop bag | |
| 12.7 | South Lake | Water only | 4.6 | Crew outbound only | |
| 17.3 | Island View | Full | 6.9 | ||
| 24.2 | Warm Springs | Full | 5.4 | 12:30 PM | Crew, drop bag |
| 29.6 | Wulfow | Water only | 2.7 | ||
| 32.3 | Liberty Glen | Full | 4.3 | Crew, drop bag | |
| 36.6 | Lone Rock (turnaround) | Full | 4.3 | 4:15 PM | |
| 40.9 | Liberty Glen | Full | 2.7 | Crew, drop bag | |
| 43.6 | Wulfow | Water only | 5.4 | ||
| 49.0 | Warm Springs | Full | 6.9 | 8:00 PM | Crew, drop bag |
| 55.9 | Island View | Full | 4.6 | 10:00 PM | |
| 60.5 | South Lake | Water only | 1.6 | ||
| 62.1 | Finish | Midnight |
For the 50K, aid is at South Lake (2.4, water only), Island View (7), Warm Springs (13.9, cutoff 12:30 PM, drop bag), Wulfow (19.3, water only), Liberty Glen (22, cutoff 3:15 PM, crew and drop bag) and Bummer (27.8), with the finish at 31.1 by 6:30 PM. The race warns of "fairly long stretches between aid stations," and the longest is the 6.9 miles from Island View to Warm Springs in both races. The Half has aid at Oak Knoll (3.6), Archery (6.2, cutoff 12:00 PM) and Bummer (9.7).
What to carry: The race requires at least one bottle and says "If it's warm you will likely need more than one bottle in the afternoon." Plan water by the time to the next refill, as in How Much Water Should I Carry Trail Running? The ROOT5 comes with two 500ml soft flasks (1L total), which covers the bottle rule and fits the 50K or Half. For 19 hours of 100K with a headlamp and more food, the ROOT8 has twin 500ml front flask pockets and more room. A soft flask also works as your cup at the table; see What to Carry for a Cupless Trail Race.
Cutoffs
100K: Warm Springs (24.2) by 12:30 PM, Lone Rock (36.6) by 4:15 PM, Warm Springs (49.0) by 8:00 PM, Island View (55.9) by 10:00 PM and the finish by midnight. That is 7 hours 30 minutes to the first Warm Springs, our calculation. 50K: Warm Springs by 12:30 PM, Liberty Glen by 3:15 PM, finish by 6:30 PM. Half: Archery by 12:00 PM, finish by 2:30 PM. If you need to stop, the race lists Warm Springs, Liberty Glen and, on the 100K, Lone Rock as drop points, and says "DO NOT DROP at Island View or Wulfow."
Required gear and rules
- Cupless: "All runners are required to have your own bottle, flask, reservoir." and "Every runner must carry at least one water bottle."
- 100K: "A headlamp will be required when leaving Warm Springs after 3:30pm."
- "Pacers are not allowed due to the difficulty of providing adequate aid."
- "No trekking poles!"
- "NO LITTERING. Zero, zip, nada. Carry it in, carry it out."
- Drop bags must be smaller than a shoe box, waterproof and labeled. Cutoff for drop bags is 4:45 AM (100K) and 7:15 AM (50K).
Crews can meet 100K runners at South Lake (outbound only), Warm Springs and Liberty Glen, and 50K runners at Liberty Glen. Cell service is spotty, so print the crew directions and arrive with a full tank. Note that the US Army Corps of Engineers says Liberty Glen campground "remains closed for maintenance until further notice," while the race still lists it as an aid and crew point, so check the final guide.
Weather and daylight
The race's only weather note is about heat: more than one bottle in a warm afternoon. 100K runners start at 5:00 AM in the dark and need a headlamp if they leave Warm Springs after 3:30 PM. Check sunrise and sunset for Lake Sonoma closer to race day.
Packet pickup, parking and camping
Packet pickup for all events is at Healdsburg Running Company on Thursday (12:00 to 6:00 PM) and Friday (12:00 to 7:00 PM). On race morning, 100K pickup and check in opens at 4:00 AM and 50K at 6:00 AM at the Visitor Center; the Half checks in at 8:30 AM at Lone Rock. Park in the overflow lot as directed, and fill up with gas the day before because there are no gas stations near the course. Camping is allowed Friday and Saturday nights next to the start and finish with no booking, cars or vans only, and quiet hours from 9:00 PM to 4:00 AM. Half runners get a free shuttle from the finish back to the start between 12:30 and 3:30 PM.
100K and 50K finishers receive a custom labeled bottle of Wilson Winery wine or a non-alcoholic option; Half finishers get a mug.
FAQ
Is there still a Lake Sonoma 50 mile race?
No. In 2027 the distances are 100K, 50K and the Trail Sisters Half Marathon.
Is Lake Sonoma cupless?
Yes, every distance. Carry at least one bottle, flask or reservoir.
What is the longest stretch without aid?
6.9 miles, Island View to Warm Springs, in both the 100K and the 50K.
Are pacers or poles allowed?
No. Neither pacers nor trekking poles are allowed.
Is the 100K a Western States qualifier?
Yes, with a finish under 19 hours. The homepage and UltraSignup name the 2028 Western States.
Sources: runlakesonoma.com (home, course details, schedule, rules, directions and camping pages and the linked participant guides), UltraSignup and the US Army Corps of Engineers Lake Sonoma page. Read October 12, 2026. LECAMO is not affiliated with Lake Sonoma or Trail Sisters.