Boston Marathon runners doused themselves with water at the halfway water station in Wellesley.

The Wellesley water station continued to provide relief to runners of the second-slowest Boston Marathon since 1985.

The heat in Wellesley took its toll.

Overheated runners took advantage of a water station at the halfway mark in Wellesley.

High temperatures, like those experienced at the Wellesley watering station, may have convinced thousands of entrants to skip Monday's Marathon.

Empty water cups littered the course near a Wellesley watering station.

A female runner collapsed at the halfway mark next to Wellesley College. She was immediately taken away on a stretcher by Wellesley fire department staff.

Joe Verdone hosed off overheated runners climbing Heartbreak Hill in Newton.

Harvard residents Jen Schoenberg (left) and Mary Hawes were waited on Commonwealth Avenue in Newton for Schoenberg's husband, Jon Schoenberg, who was running his 20th Marathon.

Martiza Rodriguez, from Ecuador, cooled off at water station at Heartbreak Hill in Newton.

A runner was transported across Commonwealth Avenue from the medical tent to an ambulance at Heartbreak Hill in Newton Monday.

A heated runner was helped across the finish line.

A runner was transported across the finish line.

John Ouweleen, 71, of Sebastian, Fla., was helped by medical workers when he cramped up after finishing the race.

A runner collapsed at the finish line.

American Tyrell Heaton was helped to the finish line by Canadian Jeff Fyfe, left, and American Blake Whitney.