I was quite surprised to see how cold it was when I returned home.
この場合、次のように言うと良いでしょう。
ーIt was shocking how cold it was when I got back.
「帰ってきたらすごく寒くて驚いた」
It was shocking how cold it was で「なんて寒いのかと衝撃を受けた」
ーI was quite surprised to see how cold it was when I returned home.
「帰国したらすごく寒くて驚いた」
I was quite surprised to see how cold it was で「どんなに寒いかに気がつき驚いた」
to return home で「帰国する・故郷に戻る」
ご参考まで！
カナダ 
