暑中見舞い (sho-chū-mi-mai) "Summer greetings"
In Japan there is a tradition to send gifts and cards in mid-summer, to let your loved ones know that you are thinking of them during the oppressively hot summer days.
These cards are called 暑中見舞い (sho-chū-mi-mai) cards, which is usually translated as "summer greetings".
via japanwords