Shochumimai is a summer greeting card in Japan. We used to exchange summer greeting card, though it is less popular than new years card.
It very hot and humid in summer in Japan so we think of acquaintances health. Instead of visiting, we send a card. Sometimes send a gift called お中元Ochugen, 暑中見舞いShochumimai, 残暑見舞いZanshomiai depending on when you send.
暑中 Shochu literally means in the mid hot summer, under heating hot
見舞い Mimai is often used for inquiry of health or visiting someone in a hospital or in a natural disaster in order to encourage him.
Why don’t you send a summer greeting card?
From Weblio,https://ejje.weblio.jp/sentence/content/%E6%9A%91%E4%B8%AD%E8%A6%8B%E8%88%9E%E3%81%84
Shochumimai is translated
Best wishes for the summer season.
How are you getting along with this hot weather?
I hope you are enjoying the summer.
