Sounds of summer from my childhood:

The sound of wind in birch trees.
I spent all my summers at my grandma’s summer cottage in Kiisa, together with her and my brother, and my parents for part of the summer. She had a largish garden, mostly cultivated and full of flowerbeds, a kitchen garden, fruit trees and so on.
At the bottom of the garden there was a wilder area with weeds and thistles. At the other edge of that area there was a stand of trees, mostly birches. She had a rope hammock between two of them. We used to lie in it and solve crossword puzzles together.

The sound of lawnmowers.

The distant sound of saws and hammers. I guess our neighbours were building things.

The sound of swallows.

The sound of weather reports on the radio. I cannot remember listening much to the radio much at home, but my grandma had a small battery-operated radio that she used to listen to. News reports, weather reports, other things I cannot remember.
The closest weather station to Kiisa was Kuusiku, so I knew to listen for that word. Vahelduva pilvisusega kuiv ilm. Tuul puhanguline, valdavalt lõunakaarest, 5 kuni 7 meetrit sekundis.

The sound that I currently most strongly associate with summer is the song of blackbirds. They are plentiful around here. I like sitting out on the deck in the evenings and listening to them sing.

They go to sleep before I do.