Houston Marathon

The pick for a mid-January PB: a flat course with a field of around 7,000 to 8,000 finishers, large enough for company at most paces without the crush of the biggest races. The January 17, 2027, race is already sold out, a sign of how many runners use it as a winter goal. Weather is the gamble. The organizers' historical averages are a low of 45°F and a high of 63°F, which is ideal, but some years turn warm and humid. Before the 2017 race, organizers urged runners to slow down and adjust their pace because of the forecast. Pick Houston if you can accept a race-week rethink of your goal.