It should be "今天好冷啊" instead. "多么" just sounds too "文绉绉" 了
Yes, but this section teaches how to use “么” or “多么”.
I think a better translation would be: "How cold it is today!".
多么 is also acceptable as it measures extremity of the word 冷. However, it is also acceptable to translate into 今天好冷啊 since it's commonly expressed.
Well, it's not a bad thing to teach people how to use 多么
Would a better translation be “How cold it is today!” or from Chinese, “今天好冷啊！”?