Race calendar · September 2027
137 half marathons 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 is a transition month for 13.1 racing in the United States. Summer has not fully let go in the South, the Southwest, or along the Gulf Coast, where heat and humidity can still make a race feel harder than the fitness suggests. The Pacific Northwest and the mountain states, by contrast, begin to feel like fall, with cooler mornings and more forgiving conditions.
For most runners, a September half marathon is either a summer fitness test or a bridge into a fall training block. Starting a build in mid-June puts you at the right point in a training cycle. Daylight is shortening noticeably by late September, so early race starts become more likely, and early-week shake-out runs may happen in the dark.
The calendar in September is concentrated rather than spread across the month, so your options are largely dictated by a single window. If a race near you does not work, traveling for one is worth considering, since the national spread is wide enough that a comfortable climate is almost always within reach.
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
Half marathons 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 September half marathons that stand out on the numbers: the biggest field, and the longest unbroken run of editions.
It is a lean month for the Half Marathon. September carries 137, against 376 in April and 102 in August, 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.
It depends heavily on where you are. Texas, Florida, Georgia, and the Gulf states are still legitimately hot in September, with humidity that slows paces and raises perceived effort. Start conservatively, prioritize hydration, and do not chase a time goal if conditions are bad. The northern Midwest, New England, and higher elevations in the Rockies are far more forgiving.
In the South and Southwest, treat it like a summer race: light singlet, shorts, a hat or visor, and sunscreen. In the northern states and at elevation, a light long-sleeve layer for the start is worth carrying, since mornings can be genuinely cold even when the afternoon warms. Check the local forecast the night before rather than assuming either direction.
A standard half marathon build runs roughly twelve to fourteen weeks, which means starting in mid-to-late June. That puts your hardest training weeks in July and August, the warmest part of summer. Running your long efforts early in the morning helps manage heat load. Treat those summer long runs as fitness deposits even if the paces feel slow.
Yes, if your local climate is still too hot for a comfortable race. Mountain venues in Colorado and Wyoming offer cooler air and dramatic scenery. The Pacific Northwest is typically at its best. The Midwest has a dense cluster of options.
The busiest weekend is September 18 and September 19, with 45 of them, 25 of those on Saturday, September 18. Another 4 fall on a weekday, which is worth knowing if you are traveling for one.
Across the 98 of these September half marathons with published results from past editions, the median finisher ran 2:13:52, and the median winning time was 1:27:58. So anything under 2:13:52 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 55 runners, across the 98 of these September half marathons 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 3:31:24.
Texas has 18, Florida has 10, Oklahoma has 9, Colorado has 6, Michigan has 6. If you are willing to travel, those are the states where a September weekend gives you the most to choose from.
Yes, 14 races around the United States get you off the pavement: 10 are trail races, and 4 mix road and trail.
