暑さのため

because of the heat

→ 暑さ
phrase Rare #33,945
because of the heat Expresses a cause or reason and is somewhat formal. It is often followed by に, though に may be omitted in some contexts.
JA: 暑さのため、今日は早く帰ります。
EN: Because of the heat, I'll go home early today.

私は暑さのため眠れなかった

I couldn't sleep because of the heat.

彼は暑さのため食欲がなかった

He had no appetite because of the heat.

暑さのため多くのランナーが意識を失った

Many runners lost consciousness due to the heat.

腐ったのは暑さのためです

The meat spoiled because of the heat.

私達は激しい暑さのため戸外で遊べなかった

We couldn't play outside because of the intense heat.