1. In America, when they show the temperature, people use Farenheit.
However, in our country, we use Celsius.
2. New Zealand is composed of the South Island and the North Island. It rains a lot in July and August in the mountainsides in the South Island.
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Are the sentences above grammatical?
Would you check awkward expressions?
Everything sounds fine.
If you want to be more specific, you could use other, more detailed words in place of "a lot," or you can leave it as it is.