It's gotten slightly colder.
少し寒くなってきた
It's great fun walking along the shore.
海岸を歩くのはとても楽しい（◆((米略式))ではvery funともいう）
It's great in theory, but in practice it sometimes doesn't work.
それは理論的には結構だが，実際にはときどきうまくいかない
It's great to see you again.
また会えて本当にうれしい
It's guaranteed to give anyone a hangover.
それはだれでも必ず二日酔いにする
It's handy having you around!
君がいると助かるよ
It's hard to see [say, imagine] ....
…は理解し［言い，想像し］がたい
It's high time he arrived.
彼はもう着いている［いていい］はずだ
It's his deal.
彼が親だ
It's hot in here.
この中は暑い
