The Numbers at a Glance
| Ultra finishers globally (2024) | 86,885 unique runners — up from 8,402 in 2000 |
| Ultra participation growth (2024-25) | +6.5% overall; 100-milers +9.5%; backyard ultras +17.2% |
| Western States 2026 lottery odds | ~2.6% (11,328 applicants, ~260 open spots) |
| UTMB 2026 applications | 29,000+ total; up 16% year on year |
| Acres forecast to burn in the US (2026) | 5.5 to 8 million (more than 2025) |
| Major races canceled or rerouted this summer | Fat Dog 120, Ouray 100, Silver Rush 100; Leadville 100 course redrawn |
There is a scene playing out across the mountain ultramarathon world right now that tells you everything about where the sport stands. A runner gets the lottery notification in December. Months of 4am starts, 30-mile training runs and careful gut-training follow. Travel is booked, crew is confirmed, pacers are briefed. Then, about a week before the race, a text arrives. The mountain is on fire. The race is off.
This summer, that scene played out not once or twice but across a string of the most respected ultras on the North American calendar. And the uncomfortable truth is that it is not going to stop.
First, understand how big the boom really is
The growth of ultrarunning over the past two decades is one of sport’s genuinely remarkable stories. In 2000, there were roughly 8,400 unique ultra finishers in the world. By 2024, that number had grown to nearly 87,000, with close to 125,000 individual finishes logged across the year. That is a 10x increase in participants in 24 years. No major team sport in the world can show numbers like that.
The more recent data is even sharper. Across 728 ultra events on a single US registration platform in 2025, participation grew 6.5% in one year. The longer the distance, the faster the growth: 100-milers grew 9.5% and backyard ultras, those brutal timed formats where runners complete loops until only one person is left standing, grew 17.2%. Ultramarathons were the fastest-growing segment of competitive running overall in 2025, with 15% growth in participation across the endurance market.
The lottery numbers are where the pressure becomes vivid. At the 2026 Western States lottery, 11,328 people entered for roughly 260 open spots. That is about 30 people competing for every single starting place at one race. At UTMB, pre-registrations were up 16% across the flagship race and the OCC. These are not fields that are growing. These are fields that are already full, with overflow queues longer than most events’ entire participant lists.
The general running boom is driven by Gen Z, run clubs and social media. Ultra growth has a different engine. It skews older, with runners aged 35-44 making up the largest segment. Many came through road marathons first, hit a plateau and went looking for a harder challenge. The sport rewards experience over raw speed, which means age is less of a barrier than in track or road racing. Once runners find ultras, retention is extremely high. The community is tight, the races are life-defining experiences, and the demand compounds year on year.
Now look at what is burning
The 2026 North American wildfire season arrived early, burned hot and landed squarely on the calendar that the ultra boom had built.
The Fat Dog 120 in British Columbia, a beloved multi-day mountain race in Manning Park, was called off about a week before the start date when an active fire was confirmed within 500 metres of the course, with four additional blazes burning in the surrounding complex. Runners who had traveled from across North America and internationally turned around and went home.
In Colorado, the Gold Mountain Fire burned north of Ouray and east of Highway 550, filling parts of southwestern Colorado with smoke, closing public lands and triggering a cascade of race decisions across the San Juan Mountains. The Ouray 100 was canceled nearly two weeks before race day. Leadville’s Silver Rush 100 followed. The Hardrock 100, arguably the most demanding 100-miler in North America, got its green light less than 48 hours before the start gun after weeks of daily fire monitoring. Its race director, Dale Garland, had to manage decisions across nine separate permit authorities: three towns, four counties, the Bureau of Land Management and the US Forest Service. A single fire can invalidate any one of them.
The Hardrock 100 has been canceled only four times in its history, once previously due to wildfires. This year, around 150 runners finally set off from Silverton, climbing more than 33,000 feet over 13 mountain passes in a 48-hour window. But the decision to run was not made until Thursday morning for a Saturday start. Crews, pacers and runners spent weeks in uncertainty. Meanwhile, the Ouray 100 organizers who shared the same fire situation made the opposite call, citing sections of the actual course that had already burned and the additional respiratory risk in a race where lung issues are among the most common medical problems to begin with.
Same fire. Same smoke. Two experienced race organizations, both acting in good faith, reaching different conclusions. That is how narrow the margin has become.
The Leadville Trail 100, due August 22, is running on a course that fire has already forced race directors to redraw. Organizers have confirmed they have clearance but warned that reroutes are possible and every call remains subject to daily air quality index readings. The race is happening. The mountain it runs on does not look the same as it did last year.
Why this is a structural problem, not a bad summer
The instinct when a few races get hit in one season is to call it an unlucky year. But the data points in a different direction.
AccuWeather forecast that between 5.5 million and 8 million acres would burn in the United States in 2026, more than in 2025, with the worst of the season potentially still ahead in autumn. British Columbia’s own wildfire service warned this summer of difficult-to-control fires throughout the Central and Southern Interior, which is precisely where the province’s marquee trail races are built. The corridors where ultra participation has grown densest, Colorado’s San Juan Mountains and southern BC’s interior, sit in some of the most fire-exposed terrain on the continent.
The sport expanded into that terrain deliberately. The San Juans are spectacular, brutal and unique. Manning Park is one of the most beautiful stretches of subalpine wilderness in western Canada. These landscapes are the point. They are not incidental backdrops to the races. They are the races. And those specific landscapes are warming and drying faster than the surrounding regions.
Wildfire smoke is not just a visibility problem. When you run, your ventilation rate increases significantly, meaning you inhale far more air per minute than at rest. In high-smoke conditions, that means taking in more fine particulate matter per breath, deeper into the lungs, for hours at a stretch. The Road Runners Club of America recommends canceling outdoor races when the AQI crosses 200. At a 100-miler, runners are outside for anywhere from 17 hours at the front to 30 hours or more at the back. AQI can shift dramatically across that window. Race directors are being asked to make binary go/no-go calls on conditions that are genuinely dynamic, and the medical consequences of getting it wrong fall entirely on the athletes.
UTMB is factoring in climate now and it is worth paying attention to
The biggest ultra in the world has started building the problem into its own entry system. The 2026 UTMB lottery introduced a 30% boost in draw odds for runners who committed to traveling to Chamonix without using a private car. From this edition onward, all runners also pay a mandatory carbon contribution based on their round-trip travel emissions. UTMB calculates that runner travel accounts for nearly 86% of the race’s total carbon footprint.
Whether you think this is meaningful policy or greenwashing, the move signals something: the sport’s biggest event is starting to acknowledge that the climate conditions threatening trail racing are not separate from the behaviour of trail racers. That is a conversation the ultra community is going to be having more loudly in the years ahead.
What this means if you are planning an international ultra
For Indian runners who have come through the road marathon scene and are now eyeing international ultras, this adds a planning layer that did not exist five years ago.
| Race | Location | Fire Risk Window | 2026 Status | Notes |
|---|---|---|---|---|
| Western States 100 | California Sierras | June | Ran (lottery 2.6% odds) | Smoke risk in Placer/El Dorado counties is real in hot years |
| Hardrock 100 | San Juan Mountains, CO | July | Ran (48hr call) | Gold Mountain Fire; Ouray 100 same fire, different call |
| Ouray 100 | San Juan Mountains, CO | July | Canceled | Course sections burned; canceled 2 weeks out |
| Silver Rush 100 | Leadville, CO | July | Canceled | Public land closures across course |
| Leadville Trail 100 | Leadville, CO | August | Course rerouted | Running Aug 22 on redrawn course; daily AQI monitoring |
| Fat Dog 120 | Manning Park, BC | Late July/August | Canceled | Fire within 500m of course; canceled 1 week before start |
| UTMB | Chamonix, France | August | Running (late Aug) | Lower fire risk than N America; carbon contribution now mandatory |
- Check the race’s official cancellation and refund policy before you book travel. Many races offer deferral but not refunds for force majeure situations.
- Buy travel insurance that explicitly covers event cancellation, not just flight disruption. Standard policies do not cover race cancellations due to natural conditions.
- Follow the race’s official social media from about 4 weeks out, not just their newsletter. Fire situation updates often go to social first.
- For Colorado races specifically, bookmark the Colorado Department of Natural Resources fire map and the relevant county sheriff’s office. These are where public land closures are confirmed first.
- For BC races, follow the BC Wildfire Service on X (@BCGovFireInfo) during fire season.
- Build a secondary goal race into your season. One race gone does not have to mean a season gone, but only if you registered for a backup before the entry windows closed.
The question the sport has not fully answered yet
Ultra running has, so far, answered the wildfire problem one race at a time. Each director makes the best call they can in the week before their event, with the information available, and then the sport moves on. There is no governing body setting a framework for how to make the call. There is no industry-wide cancellation insurance scheme. There is no coordinated effort to map which parts of the summer calendar are now structurally unreliable versus which remain relatively stable.
The demand side of the equation keeps growing. The entry lotteries fill faster every year. Runners train harder, spend more, travel further and commit more deeply to a single date on a single mountain. And the supply side, the mountains themselves, is becoming less predictable than at any point in the sport’s history.
That is the squeeze. And the sport is going to have to start reckoning with it at a level above the individual race director’s Thursday morning phone call.
FM Take
Ultrarunning is not in crisis. The sport is healthy, growing and producing some of the most compelling athletic stories in distance running. But it has built its calendar on terrain that is now visibly less reliable than it was a decade ago. The runners absorb this individually each time a race gets pulled. The sport needs to start absorbing it collectively.
For Indian runners planning international ultras, the message is simple: treat race cancellation risk the way you treat injury risk. Build contingencies. Get the right insurance. Do not build your entire year around a single date in the San Juan Mountains in July. The training never goes to waste. The race is no longer guaranteed.