A trail runner on a grassy ridge above a sea of clouds

Lake Sonoma 100K

Completing the 100 km course in under 19 hours qualifies a runner for the Western States 100.

Prepare for Lake Sonoma 100K

A plan built from your answers and your race date.

trail training plan

The Lake Sonoma 100K is run around Lake Sonoma near Geyserville in northern California. The trails follow the lake's deeply indented shoreline, delivering a constant succession of short climbs and descents across wooded hills. A Californian spring can bring cool conditions or days that are already properly warm.

Since its relaunch the race is no longer the historic Lake Sonoma 50 but a 100 km event, which matters if you knew the old format. 1 km. Finishing the 100 km in under 19 hours counts as a Western States 100 qualifier.

The formats

3 formats on the program.

Format	Distance
100K	62 mi
50K	31 mi
Trail Sisters Half Marathon	13.1 mi

Organizer information, checked on September 21, 2026 · runlakesonoma.com

When to start

A build for this distance usually runs 12 to 24 weeks. Counted back from race day, that puts the start somewhere between October 19, 2026 and January 11, 2027.

These ranges are working conventions, not a research finding — no trial has compared plan lengths against each other. What matters more is that the plan was built for the weeks you actually have, rather than shrunk down from a longer one.

How to choose your start date

When to start

October 19, 2026

→ January 11, 2027

Worth reading before you enter

Races and distances Trail distances: what changes off the road Distance stops being the useful number. What decides a trail race is how long you are out, how much you climb, and how much the descents have wrecked your legs by the end. Read Training Eating and drinking: what’s proven, what isn’t This is where confident advice most often runs ahead of the evidence. Some of it is well tested. Some is opinion wearing a number. And one common habit can kill you. Read Races and distances When to start preparing your race Most plans fail before the first session, because the block started too late and everything had to be squeezed. Counting back from the date is the dullest and most useful thing you will do. Read

Questions

What is the date of Lake Sonoma 100K in 2027?

Lake Sonoma 100K is run on Saturday, April 10, 2027 in Geyserville. Date published by the organizer, checked on September 21, 2026.

Is Lake Sonoma a Western States qualifier?

Yes. Finishing the 100 km course in under 19 hours counts as a qualifying performance for the Western States 100. The exact conditions are published each year by the organisers on the official site.

Is Lake Sonoma still a 50-mile race?

No. Since the event was relaunched it is no longer run over the historic Lake Sonoma 50 format but as a 100 km race. A 50K and a half marathon now round out the programme.

Other races

This list keeps growing; it draws no line. A race that is missing is prepared for in exactly the same way.

Honolulu · United StatesUltra HURT 100 Jan 16 Its five-loop, 20-mile-per-lap format carries a famously high drop-out rate. Bandera · United StatesUltra HOKA Bandera Endurance Trail Race January The HOKA Bandera Endurance Trail Race is a trail and ultra weekend held in Bandera, Texas, inside the Hil Moab · United StatesUltra Moab 240 Endurance Run January 7 km ultramarathon with 9,620 m of vertical gain, run as one continuous loop out of Moab, Utah. It is par Your race is not here? Tell us about your race You can prepare for it all the same. Any race, anywhere, and even a goal without a race.

Your race is on the calendar. Your plan should be too.

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