1) Aestival 2) Appropriate to summer 3) Concerning summer 4) Of or occurring in summer 5) Of summer 6) Of the season 7) Of the summer 8) Pertaining to summer 9) Relating to summer 10) Summerlike 11) Summery Found on https://www.crosswordclues.com/clue/estival
Relating to or occurring in the summer. ... Synonym: aestival. ... Origin: L. Aestivus, summer (adj.) ... (05 Mar 2000) ... Found on http://www.encyclo.co.uk/local/20973
Es'ti·val adjective , Es'ti*vate intransitive verb , Es`ti*va'tion noun Same as Æstival , Æstivate , etc. Found on http://www.encyclo.co.uk/webster/E/69