Relating to or occurring in late summer.
The word serotinal makes people think of the end of summer, warm days, and the changing of the seasons.
Examples:
The serotinal weather makes me want to go outside.
We went for a walk in the serotinal evening.
The serotinal flowers are blooming in the garden.
I love the serotinal time of year, it's so warm and nice.
During the serotinal season, the days are long and the nights are warm.
The serotinal sunsets are so beautiful, they make me happy.