"It is hot in the South this time of year."
Translation:Det er varmt i syden på denne tid af året.
Ok So I just verified my solution with my Danish friend. A better way to think of this sentence in English where is makes sense with the Danish translation is : It is hot in the south at this time of the year. Then we can see why på and året are used. This would have been a much better example to use for this translation.
Small difference: "denne tid af året" might be limited to a single month, while "denne årstid" refers to the entire three-month season.
In certain contexts, we capitalise North, South, East, and West in English. If you're using one of them as a proper noun, it's capitalised, but if you're simply using it for direction, it's not. In this sentence, since 'the South' is referring to a place/a proper noun, it's capitalised. The comment with the American example is one such example of this, but certainly not the only example.