Despite the 38 degree rainy weather and a headwind of 10 miles per hour on Monday, 30,087 participants — runners, wheelchairs and hand cyclists — were signed up to participate in the 122nd Boston Marathon.

Among more than 30,000 other runners on Monday afternoon, Geoffrey Kirui and Edna Kiplagat, both from Kenya, finished first in the men’s and women’s elite divisions, respectively, in the 121st...