cet été-là -- that summer (there)
Adding -là (or -ci) adds a "there/that" (or "here/this") to the object. There is a kwiziq lesson on that: use-ce-cet-cette-ces-duration-la-ci-to-express-that-those-or-this-these-duration-demonstrative-adjectives
Cet manteau-là est à moi. -- This coat over there is mine.
Je prefère ce pull-ci à celui-là. -- I prefer this sweater here over that one there.