Summit Line

⏵ Course guide · California ultra

Folsom 100 Course Guide

The Folsom 100 is one big clockwise loop around Folsom Lake, starting and finishing at Granite Bay and tagging Loomis, Auburn, Cool, Salmon Falls, El Dorado Hills, and Folsom along the way. It is one of the more runnable NorCal hundreds, but the evening start, the August heat, and a stretch of road miles make it its own kind of hard. I will walk you through the loop first, then give you a pacing, crew, and fueling plan that fits a hot night-into-day hundred. There are free calculators along the way to dial in your own numbers.

⏵ At a glance

Folsom 100 quick facts

Date
Friday, August 7, 2026 (evening start)
Location
Granite Bay Main Beach, Folsom Lake State Recreation Area, Granite Bay, CA
Distances
100 miles, 54 miles, 20 miles, plus a 2-person 100-mile relay
Elevation gain
Not officially published; rolling foothill loop with a couple of real climbs (Cardiac Hill, Meat Grinder, K2)
Start
100-mile start around 7:00 PM (confirm the current year)
Cutoff
34 hours for the 100 miles
Qualifier
No Western States, Hardrock, or UTMB Running Stones status listed by the race

These facts come from the race organizer and UltraSignup. The date, start time, cutoffs, aid stations, and course can change year to year, so check the current race-day details before you commit.

The course: one loop around the lake, won and lost in pieces

This is not a course with one defining mountain. It is a 100-mile ring around Folsom Lake on mostly unpaved single-track and fire road (the race calls it roughly 85 percent trail), with rolling foothill terrain, a handful of named climbs, and a real road section in the middle. The day breaks into three very different races: the night, the hot middle, and the long grind home. Get the order of operations right and it is a friendly hundred. Get greedy early and it bites.

The night: bank cool miles, do not bank effort

Because the 100 mile starts in the evening, you are running into full dark almost right away, climbing Cardiac Hill up toward Auburn Overlook on fresh legs while it is cool. This is the gift of the course, and it is also the trap. The temptation is to feel great in the dark and run the early climbs hard. Do not. You want to reach daylight with your legs intact, because the heat is coming and the back half is long.

Practical stuff matters more than fitness here: a light you trust, a backup light, and a layer for the cooler hours. Keep your eyes down on the rocky single-track, keep your effort easy, and treat the whole first night as setup for the day, not a chance to put time in the bank.

The hot middle and the road miles

Somewhere in the middle of the loop the course throws you a stretch of pavement (roughly 10 road miles), and it tends to arrive in the hot part of the afternoon when you are already tired. Hard surface, no shade, full sun. This is where a lot of days unravel. Slow down, keep drinking, keep eating, and get your sodium up. A reflective vest is required on the road, so have it in a drop bag and ready.

The named climbs out here (the Meat Grinder, K2 up near Cool, the punchy stuff between aid) are not huge on paper, but they hit different in the heat with 50-plus miles on your legs. Hike them with purpose, keep your core temperature down, and remember that getting through the hot middle in one piece is the whole game. You cannot win Folsom in the afternoon, but you can absolutely lose it.

The long way home to Granite Bay

The back portion is a long return toward Granite Bay, including an out-and-back feel to Magnolia and back through Skunk Hollow before the final push past Browns Ravine. By now you are into a second night, the heat has broken, and it becomes a moving-forward problem more than a fitness problem. The last few miles include some paved trail and sidewalk into the finish, so keep a light on and keep your feet turning.

This is where the 34-hour cutoff earns its keep. It is generous, but only if you keep moving. The runners who finish well here are the ones who never fully stop: short, sharp aid stops, steady walking when they cannot run, and a refusal to sit down for long. Plan your crew and pacer for exactly this part of the day.

Pacing strategy for a hot, rolling, night-start hundred

Folsom rewards even effort over a flashy plan. The course is runnable, which is exactly why people overcook the early miles in the cool dark and then crawl through the hot afternoon. Run the climbs by feel, walk with purpose, and build your time chart around the heat, not against it.

Pace by grade and heat, not by your flat splits

Your road pace means very little on the rolling Folsom loop, and even less once it is 95 degrees out. What matters is grade-adjusted effort: hold an easy, sustainable output up the climbs, hike the steep punchy ones without guilt, and let the runnable flats and gentle downhills be where you actually move. The classic Folsom blowup is running the first night too hard because it feels easy and cool, then paying for it all afternoon. Use a grade-adjusted pace to turn your real fitness into honest climbing targets so you do not torch the early miles.

Build a finish prediction that respects the cutoff

Do not guess your Folsom finish off a road 100 time or a flat training block. The heat, the road miles, the night, and the rolling vert all add real time, and you want a realistic window so you can work backward into the aid stations and the 34-hour cutoff. A vert-aware finish prediction gives you a per-segment plan, so you know how much buffer you actually have at Auburn Overlook, at Cool, at Skunk Hollow, instead of finding out the hard way late at night.

⏵ Free tools to pace this course

Fueling strategy for the heat and the long haul

You are out here for the better part of a day and a night, through cool dark and serious August heat. That makes carbohydrate, sodium, and fluid every bit as important as your legs. The runners who fall apart at Folsom usually stop eating in the heat, not because they ran out of fitness.

Carbs: keep eating, especially when it is hot

Over a hundred miles, aim for a steady carbohydrate intake of roughly 60 to 90 grams per hour, and only push the higher end if your gut is trained for it. The heat is the enemy of appetite: when it is 95 degrees out and you feel queasy, that is exactly when you have to keep getting calories down. Lean on easy, cool, drinkable carbs in the hot afternoon (think fluids, chews, and real food you can stomach) and practice your exact race-day carb rate on long hot training runs so it feels normal, not like an experiment at mile 60.

Sodium and fluid: built for the day and the road

In the August heat, lean toward the high end on sodium, often around 500 to 700 milligrams per liter of fluid, and more if you are a heavy or salty sweater. Carry enough fluid to cover the hot, exposed stretches (the road section especially) instead of arriving at the next aid empty and behind. Then swing the other way at night: it cools off, so do not over-drink in the dark hours. Weigh yourself before and after a hot long run to find your real sweat rate, and build the plan around your own number, not a generic one.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Folsom heat with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

⏵ Train for it with Summit Line

Get a race-day plan built around YOUR fitness, this exact Folsom 100 loop, and your projected splits. Summit Line reads your real training, builds a plan for the rolling climbs and the heat, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

Folsom 100 FAQ

How hard is the Folsom 100?

The Folsom 100 is a real 100 miler, but it is on the more runnable end of the NorCal hundreds. It is a single big clockwise loop around Folsom Lake on mostly foothill single-track and fire road, with rolling hills and a couple of genuine climbs (Cardiac Hill, the Meat Grinder, K2 up in Cool) rather than one giant mountain pass. The catch is the format: a roughly 7 PM Friday start means you run into the night almost immediately, the August heat lands on you the next afternoon, and there is a stretch of road miles in the middle. The 34-hour cutoff is generous, so a prepared runner who can keep moving and manage the heat has plenty of room to finish.

How much climbing is in the Folsom 100?

The race does not publish an official total elevation gain, so be careful with any single number you see (GPS watches disagree a lot on this lake). What you can count on is that this is rolling foothill terrain, not a high-alpine grind. The vert comes in repeated short, punchy climbs and a few named ones (Cardiac Hill on the way up to Auburn Overlook, the Meat Grinder, K2 near Cool), not in one long sustained ascent. Treat it as a course where the climbing nibbles at your legs all day rather than one big climb you can brace for.

What time does the Folsom 100 start, and why an evening start?

The 100 mile has gone off in the evening, around 7 PM on the Friday, which is unusual but on purpose. Because the loop runs clockwise around Folsom Lake in the August heat, starting at night lets you bank cooler, shaded miles in the dark before the sun is a problem. The trade-off is you are running through the night on fresh legs, then you hit the hot middle of the course (including the road section) the following afternoon when you are already tired. Always confirm the exact start time for the year you are running, since it can shift.

What are the cutoff times and aid stations for the Folsom 100?

The 100 mile has a 34-hour overall cutoff, which is roomy for the distance. The loop is supported by a string of aid stations roughly every 5 to 11 miles, with named stops like Rattlesnake, Cardiac Hill, Auburn Overlook Park, Cool, Rattlesnake Bar, Skunk Hollow, Magnolia, and Browns Ravine on the way back to Granite Bay. Drop bags are typically allowed at a few of them (Auburn Overlook, Cool, Skunk Hollow), and pacers can join from Auburn Overlook. Confirm the current aid-station list, spacing, and any intermediate cutoffs in the race-day details before you start.

Do I need a crew, pacer, or drop bags for the Folsom 100?

You can finish self-supported off the aid stations and drop bags, but a crew and a pacer make a hot night hundred a lot more manageable. Drop bags get you to a few key points (Auburn Overlook, Cool, Skunk Hollow), so stash lights, a jacket for the night, sunscreen and extra fluid for the day, and your backup nutrition. Pacers are allowed starting at Auburn Overlook, which is exactly when company helps: through the late night, the hot afternoon, and the long grind back toward the finish. A reflective vest and a light are required on the road and at night, so pack those no matter what.

What is the terrain and weather like at the Folsom 100?

It is mostly unpaved (the race describes it as around 85 percent trail) on the single-track and fire roads that ring Folsom Lake, with a real road stretch in the middle (roughly 10 miles of pavement) that tends to land in the hot part of the day. Early August in the Sierra foothills is hot and dry, often well into the 90s in the afternoon, then it cools off at night, so you are dressing for two very different races in one. Plan for full dark on the front end (lights, a layer) and for serious heat management on the back end (fluid, sodium, sun cover). Confirm conditions and any course changes with the race before you go.

This guide is independent and for planning only. The course details, dates, start time, cutoffs, and aid stations come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.