The Collaborative International Dictionary of English v.0.48:
Summery \Sum"mer*y\, a. Of or pertaining to summer; like summer; as, a summery day. [1913 Webster]WordNet (r) 3.0 (2006):
summery adj 1: belonging to or characteristic of or occurring in summer; "summery weather"; "summery dresses" [ant: autumnal, vernal, wintery, wintry]