Leadville 100 Reroutes Its Course Due to Wildfire
For the first time in its 42-year history, the Leadville Trail 100 will not run its original course. The Willow Fire, burning actively west of Leadville, Colorado, has forced race organizers to redesign the route for both the Leadville 100 Run and the Leadville 100 MTB events. If you're registered, or if you follow ultrarunning at all, this is a moment worth paying attention to.
This isn't a minor tweak. It's a fundamental reroute of one of the most storied courses in endurance sport, driven by conditions that no amount of race preparation could have anticipated.
What the Willow Fire Is Doing to the Race
The Willow Fire ignited west of Leadville in Lake County, Colorado, and has been burning aggressively enough to threaten the safety of key sections of the traditional Leadville course. Race management confirmed that portions of the original route pass through or adjacent to fire-affected terrain, making it impossible to guarantee runner and crew safety along those segments.
Organizers acted quickly. Rather than cancel the event outright, they worked with local authorities, land managers, and the U.S. Forest Service to identify an alternative route that preserves the spirit of the race while keeping participants out of harm's way. The result is a modified course that still takes place at altitude in the Colorado Rockies, but follows a different path than the one runners have trained on for months.
For context: the Leadville Trail 100 Run covers roughly 100 miles of high-altitude terrain, with a starting elevation of around 10,152 feet and a maximum elevation near Hope Pass of approximately 12,600 feet. The course has been the same since the race launched in 1983. Changing it now is not a small administrative decision. It's a historic one.
Why This Is a First for Leadville
Leadville has survived economic downturns, extreme weather, and the kind of organizational growing pains that come with managing thousands of registered athletes. But in over four decades of running, it has never altered its course because of an environmental emergency.
That changes this year. And what makes this moment significant isn't just the logistical challenge. It's what it represents. Wildfire seasons in the American West are growing longer and more destructive. The National Interagency Fire Center has documented a clear upward trend in both the number of large fires and total acreage burned across western states over the past two decades. Race directors who built their events around fixed geography now have to reckon with the fact that geography itself is becoming less predictable.
Leadville isn't alone in this. Trail races across California, Colorado, Oregon, and Montana have dealt with last-minute cancellations or reroutes in recent years due to fire conditions. But Leadville doing it, for the first time, at this scale, sends a signal across the sport. Climate conditions are now a permanent variable in race planning, not an occasional disruption.
For a broader look at what's happening across the sport right now, Ultra Running: The Biggest News This Weekend tracks the latest developments across major ultramarathon events this season.
What Registered Runners Are Facing Right Now
If you're toeing the start line this August, here's what's immediately relevant. The course you trained for is not the course you'll be running. That creates three distinct challenges: pacing strategy, crew logistics, and aid station placement.
Pacing strategy is the most complex issue. Experienced Leadville runners have often memorized the original course down to the mile. They know where the climbs get steep, where they can push, where they need to hold back before Hope Pass. That knowledge doesn't transfer automatically to a rerouted course. You're effectively running blind on sections you haven't studied, at altitude, after 50-plus miles on your legs.
If you haven't already thought through your approach to the new elevation profile, How to Pace a Hilly Summer Race Without Blowing Up is worth reviewing before race week. Managing effort on unfamiliar climbs at 10,000-plus feet is where a lot of runners will either save or lose their race.
Crew access is the second major variable. The original Leadville course has well-established crew points that families and pacers have used for years. On a rerouted course, those access points may shift, move entirely, or require longer drives between locations. Check the official race communications closely and confirm your crew knows the updated checkpoint locations before you arrive in Leadville. Don't assume anything transfers from previous years.
Aid station logistics are also in flux. Organizers are working to ensure aid station coverage on the new route, but spacing and placement will differ from what returning runners are used to. If you've built your nutrition and hydration plan around specific mile markers, revisit those calculations with the updated distances in mind.
How to Prepare in the Days You Have Left
You're not going to be able to train on the new course before race day. That's just the reality. But there are things you can do to close the gap between preparation and the unknown.
Study the new course map as thoroughly as you can. Look at elevation profiles, not just mileage. Identify where the major climbs happen relative to the aid stations, and adjust your fueling windows accordingly. At 100-mile distances, a miscalculation on caloric intake compounds quickly over the back half of the race.
Nutrition during high-altitude ultras puts significant demands on your body. Inflammation, oxidative stress, and impaired recovery are real physiological factors at elevation. Research published across large population studies has highlighted how deficiencies in key micronutrients can amplify inflammation markers. Make sure your pre-race nutrition protocol is dialed in, not improvised.
Healthy fat intake also matters more than many runners acknowledge at this distance. Avocado, Healthy Fats, and Performance: What Active Adults Should Know covers why fat-adapted energy becomes relevant when you're running for 20-plus hours. It's not glamorous prep, but it's practical.
Protein intake in the days before also affects how well your muscles hold up during and after the effort. How Much Protein Do You Actually Need Based on Your Activity Level? gives a clear breakdown for endurance athletes operating at high volume.
Beyond nutrition, adjust your mental framework. The runners who struggle most with reroutes are often those who can't let go of the original race plan. The course has changed. Your job is to race the course that exists, not the one you memorized. Flexibility in execution, while maintaining discipline in effort, is what gets you across the finish line.
What This Means for Ultrarunning Going Forward
The Leadville reroute is going to generate conversation well beyond 2026. Event directors across the sport are watching how Leadville's organization handles this, both logistically and in how they communicate with athletes. Transparent, fast communication has been critical here. Runners need lead time to adjust training, crew plans, and travel logistics. Any delays in that communication cost athletes something real.
It also raises a longer-term question about course certification, records, and qualification standards. The Leadville 100 serves as a qualifier for events like the Ultra-Trail du Mont-Blanc (UTMB). Whether a rerouted course retains its full qualification status is the kind of detail that matters to athletes who registered with a specific competitive goal in mind. Race organizers and governing bodies will need to clarify this quickly.
For runners who are using Leadville as a stepping stone toward fall goals, whether that's recovery, a PR attempt at a shorter distance, or simply building confidence, How to Set a Personal Best This Fall outlines how to convert a hard summer race into fall momentum regardless of how the race unfolds.
Wildfire conditions in the American West aren't going to ease. The 2026 fire season has already been notable for its early start and geographic spread. Race organizers in mountain and high-desert environments are going to have to build contingency planning into their annual calendars the same way they plan for weather or permit renewals. Leadville has now shown it can adapt under pressure. That matters.
The Bottom Line for Registered Athletes
If you're running Leadville this August, you're navigating something genuinely unprecedented. The course is different. The logistics are different. The mental preparation required is different. None of that means the race is less meaningful. In some ways, adapting to what the course actually is, rather than what you expected, is exactly what ultrarunning asks of you.
Stay close to official race communications. Update your crew. Revisit your pacing and fueling plan with the new elevation profile in mind. And respect the conditions that forced this change. The Willow Fire is still burning. The people managing this event made a hard call to protect you while still giving you a race. That's worth acknowledging at the start line.