Unlike many characters in "The Lottery," we find out quite a bit about Mr. Summers. We know he's married to "a scold" and has no children. The villagers feel sorry for him—even though he runs a lucrative coal business and has plenty of spare time:
[...] [He has] time and energy to devote to civic activities (like the square dances, the teen club, the Halloween program, and of course, the lottery). (4)
This tells you something about both Mr. Summers himself and the priorities of the villagers: they appear to place more emphasis on a traditional family life than on the kind of worldly success that Mr. Summers has achieved.
We also learn that Mr. Summers is quite the innovator: he wants to make a new black box because the old one is getting shabby, a suggestion the villagers don't take to:
[...] no one liked to upset even as much tradition as was represented by the black box. (5)
He's had more success getting the villagers to use strips of paper instead of chips of wood when drawing for the lottery. He introduces this notion in the name of progress, pointing out that chips of wood may have been fine when the village was small, but now that the population is growing, they needed to use something that would fit more easily into the box. Mr. Summers is the face of progress in the village; he works wholeheartedly to give the lottery a new face for the 20th Century.
It's also worth pointing out that his name is identical to the season in which this story is set. The fact that the lottery takes place in the summertime irrevocably links Mr. Summers to the whole nasty tradition.