The fastest half marathons in the USA for a personal best

A half marathon PR needs three things on the day: a flat course, cool air and people to run with. The US has plenty of all three, but not always at the same race, and “fast and flat” is on almost every race’s website. So this guide starts from the data: the climb and race-day weather of 133 upcoming US road half marathons, and real finish times where we have them.

Flat, cool courses for a PR

These have 50 m of climbing or less, no big net drop, and a usual start of 12°C (54°F) or below that stays under 18°C (64°F) while you run. They are ranked by climb and how close the start is to about 8°C, where most runners are fastest.

“Climb” is the total elevation gain. “Usual start temp.” is the 10-year average at the start time on race day. “Top-10 avg” is the average finish time of the 10 fastest men and women over recent editions, where we have results. Dates marked “est.” are not yet confirmed.

10 of these 15 races are between November and March, when the South is cool: Texas, Arizona, the Gulf Coast and the Carolinas have some of the best PR conditions in the country in winter, while the North is cold and often icy. In spring and autumn, the Midwest and the Northeast take over.

Where the fastest fields race

Ranking races by how fast the top 10 finish tells you where the competition is. That reflects the course, but also prize money and elite fields, so read it as “where you will have fast runners around you” rather than a pure measure of the course.

Big, fast fields help in their own way: there are groups to run with at almost every pace, and many of these races have pacers. Start in the corral that matches your goal time, and don’t let the first mile pull you out too fast.

Downhill half marathons

Some of the fastest-looking times in the US come from courses that drop hundreds of metres from start to finish, often down a mountain canyon. Gravity really does help, but a long descent pounds the quads, and you need to train on downhills to make it pay. Times on these courses are also not eligible for records: World Athletics and USATF require that a course drops no more than 1 m per kilometre from start to finish.

Making the most of a fast course

• Check the forecast, not just the average. A 10-year average start of 8°C still leaves room for a warm, humid or windy year. Race pages show how much race-day weather varies year to year.
• Mind the wind on coastal courses. Flat beachfront routes are fast in still air, but an out-and-back into a headwind costs more than it gives back.
• Pace the first mile. On a flat course, an even pace is fastest. Set a target with the race time calculator, which adjusts for climb and temperature.

Quick answers

What is the fastest half marathon in the USA?

By results, Houston Half Marathon, where the top 10 run the fastest times of any US half we track. It is also flat and usually cool, so it’s fast for everyone else too.

What is a good half marathon course for a PR?

Under 50 m of total climb, a start around 5 to 12°C, few sharp turns and a field big enough to run in a group. Every race page on iRun42 shows the climb, the course profile and the usual race-day weather.

Do downhill half marathon times count?

They count as your time, and most races accept them for corral seeding. They are not eligible for records, and some race entries that use qualifying times treat big-drop courses differently, so check the rules if a time matters for entry.

For the flattest courses worldwide, see the flattest half marathons; for Europe, the fastest half marathons in Europe. New to the distance? Start with how to choose your first half marathon.