I'd totally die in the heat with 〜じゃう

Grammar Explanation: Doing completely or ending up doing with 〜てしまう and 〜ちゃう

On a summer day, Hori and her friends in class can’t ignore the heat.

由紀(ゆき):: 「外(そと)の暑(あつ)さってなんなの…？　クーラーないと死(し)んじゃうって…っ」; “What's with this heat outside...? I'd totally die without the AC...”; 「この日差(ひざ)しのなか体育(たいいく)とか絶対(ぜったい)無理(むり)だわ…」; “There's no way I can do PE in this blazing sun...”

Key Points

死(し)んじゃう = “I’ll end up dying”
- 死(し)んじゃう is the casual spoken contraction of 死(し)んでしまう, from 死(し)ぬ + 〜でしまう
Why じゃう follows ん
- For verbs whose て-form ends in で, 〜でしまう contracts to 〜じゃう in casual speech.
- 死(し)ぬ becomes 死(し)んで, then 死(し)んでしまう becomes 死(し)んじゃう.
クーラーないと sets the condition
- クーラー(が)ないと means “if there is no AC” or “without the AC”; the subject marker が is omitted in casual speech.