Summer Solstice
noun, の adjective
If you have attained summer, that must mean you finished out with the previous season and are going into summer. This is the summer solstice.
You didn't learn this reading of 夏 with the kanji, so here's a mnemonic to help:
Just think about how cute little geckos (げ) start to come out into the open during the summer solstice. It's too cold for them to be out in the open before that, so if you look outside at the right time, you'll see geckos popping out of the ground all over the place!
父に夏至から11日目のことを何と呼ぶか知っているかと聞かれたので、得意気に「ハゲ症」って答えたんですけど、それって「ハゲ頭の症状」って意味になるみたいで。父は笑って、正しい答えは「半夏生」だよって教えてくれましたけどね。
My dad asked me if I knew what to call the eleventh day after the summer solstice, so I said triumphantly "hageshou," which literally means "baldness-symptom". He laughed and told me the correct answer was "hangeshou."