I think that summer vacation should be longer that than winter vacation.

First, winter is too cold, so I can't play (a lot) outside a lot. But I can play (a lot) outside a lot in summer. So I should have longer vacation in summer when I can play a lot outside. So if I have longer vacation in summer, I can play a lot outside.

Second, I like swimming. I can go to a swimming pool, (to the) beach or  (to) Water Park in summer. If I have longer vacation in summer, I can go to many places where I can (enjoy) swim(ming)

Third, I don't want to study when it's too hot. I can't concentrate on studying at school in hot weather. Therefore, So I want to have a longer vacation in hot summer so that I can stay at home.

I can play outside a lot, go to a swimming pool, beach or waterpark and I don't want to study in hot weather, so (These are the reasons why) I think summer vacation should be longer than winter vacation.

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