"It's cold tonight" 是描述今天晚上很冷的常用说法。
其中的 "it's" 是缩写，表示 "it is"，而 "tonight" 是表示 "今晚" 的词。
例如:
"It's cold tonight, I think I'll wear a jacket." (今晚很冷，我想我要穿上夹克)
"I hope it's not as cold tonight as it was last night." (我希望今晚不像昨晚一样冷)
"I'm glad it's not as cold tonight as it was forecasted to be." (我很高兴今晚不像预报的那样冷)