I hope that you're doing fine [well] in these days of hot summer!《レ》
I hope you are staying cool in this summer heat!《レ》
Midsummer greetings.
暑中見舞であれば、(普通のはがきに)決まり文句の「暑中お見舞申し上げます」と書けばよい。
With summer greeting cards, you can use a set phrase "Shochuuomimai moushiagemasu" (Please take care of yourself in the hot summer).〔【出典】Hiragana Times, 2004年8月号◆【出版社】株式会社ヤック企画 〕"HT214028", "2570651"