aestival

/ˈiːstɪv(ə)l/
/iːˈstʌɪv(ə)l/
/ˈɛstɪv(ə)l/
/ɛˈstʌɪv(ə)l/

adjective

Belonging to or appearing in summer.

He grouped species into ephemeral, aestival, and evergreen.