Race calendar · September 2027
13 ultramarathons across the US in September 2027, sorted by date. Which weekends are busiest, what the fields actually run, entry fees, and where each one starts.
September ultras in the US land in a true shoulder season. Mountain and northern venues are moving into their best fall conditions, with cooler air and reliable footing, while races in the South and lower elevations can still carry real heat and humidity, especially in the first half of the month.
The calendar here is tight, and nearly everything clusters into a single late-September weekend. That concentration gives you a clear target date to build toward, but it also means your backup options are slim if a race fills or your schedule shifts. Book early and have a plan B.
For most runners, a September ultra marks the first serious goal race after a summer of heat training. The distance demands a full build, so think carefully about whether your training has prepared you for what the course profile and conditions will ask, not just for covering the miles.
What the field actually runs
How we calculate these stats: RunSesh calculates these figures from the most recent published results of past editions, sourced from RunSignup. We show aggregates only: field size, winning and median times, and the cutoff. We never publish individual finisher tables. Last updated Nov 12, 2026.
When in September
Ultramarathons are not spread evenly across September. Here is how the calendar actually falls, weekend by weekend, which is the part worth knowing before you book a trip or plan a taper around one.
By the numbers
The largest field of any September Ultra, from the most recent published results.
It is a lean month for the Ultra. September carries 13, against 37 in April and 7 in July, the quietest. A September race is worth planning around rather than picking late, because the one that fits your training block may be the only one within reach.
Dress for range. Morning starts can be cool in mountain and northern venues while midday heat lingers in the South and mid-Atlantic. Carry a light layer for early miles, plan for sun exposure through the afternoon, and check whether your race is remote enough to require mandatory gear at aid stations.
Yes, especially in the South and Southeast. Alabama and Texas races on the calendar can see real heat and humidity into late September. Mountain venues in Colorado and Alaska are another story entirely. Know your specific race location before finalizing a pacing or hydration strategy.
Most ultra training cycles run four to five months, which puts your base-building start in spring. For a late-September race, beginning structured training in late April or May gives you time to peak through summer heat and taper into race-ready shape without carrying fatigue from an overly long build.
It depends on the race. The range of distances and entry fees on the September calendar is wide, from accessible trail fest formats to hundred-milers with serious cutoffs. First-timers should look closely at cutoff times, elevation, and aid-station spacing before committing, not just at the mileage on the label.
The busiest weekend is September 25 and September 26, with 4 of them. Another 4 fall on a weekday, which is worth knowing if you are traveling for one.
Across the 6 of these September ultramarathons with published results from past editions, the median finisher ran 8:23:23, and the median winning time was 5:14:28. So anything under 8:23:23 puts you in the faster half of a typical field. That is the middle of these RunSignup fields, walkers and charity entrants included, not a national average.
The median one finished 66 runners, across the 6 of these September ultramarathons with published results from past editions. Most are far smaller than the big-city events people picture, which means less crowding at the start and a friendlier field, with a last recorded finisher at 11:27:28.
California has 2, Florida has 2, Montana has 2. If you are willing to travel, those are the states where a September weekend gives you the most to choose from.
Yes, 7 races around the United States get you off the pavement: 6 are trail races, and 1 mixes road and trail.
