Used attributively before a noun to describe something characteristic of summer.
Light fabrics like cotton are perfect for summertime wear.
Les tissus légers comme le coton sont parfaits pour une tenue estivale.
Used informally to mean 'during the summer'.
They rent out their cottage wintertime and stay there themselves summertime.
Ils louent leur chalet en hiver et y séjournent eux-mêmes en été.
Synonyms
in summer
in the summer
during the summer
during summer
throughout the summer
in the summertime
over the summer
during the summer months