Source : Webster's Revised Unabridged Dictionary (1913)

Summery \Sum"mer*y\, a.
   Of or pertaining to summer; like summer; as, a summery day.

Source : WordNet®

summery
     adj : belonging to or characteristic of or occurring in summer;
           "summery weather"; "summery dresses" [ant: {autumnal},
           {wintry}, {vernal}]