Twelve weeks from Sunday is August 2. That is enough runway for a healthy adult to build to a half marathon, and August is the last reliable month before fall races crowd the calendar. [1]

Hal Higdon's Novice 1 plan — the de facto starter for first-time half-marathoners — runs twelve weeks, peaks at a ten-mile long run two weekends before race day, and asks for three weekday runs of 30 to 45 minutes. [1] The long run is on Sunday. Higdon notes the day is movable, but the design is not: one progressively longer effort each week, sandwiched between a rest day and a cross-training day. [1] Nike's plan and most marathon-handbook plans anchor Sunday for the same reason — it is the day adults can give an unbroken two-hour block to. [2]

The May part is the heat. A Boston runner who races in August has six weeks to acclimate to a 75°F dew point, and the only way to do it is to run in 75°F dew points. [2] The first week of acclimation is the worst — heart rate at threshold paces, sweat rate doubled, perceived effort climbing — and the runners who skip it run their slowest race of the year. The protocol is conservative: add ten minutes per week to the long run; do not add intensity in the same week; drink to thirst; do the run before 7 a.m. for the first three weeks of June.

Sixteen-week marathon plans starting Sunday land on August 23 — late August, where the cool mornings begin to outnumber the hot ones. The Sunday long run is the discipline; the August race is the reward.

-- NORA WHITFIELD, Chicago