Watermelons are a good source of vitamins (A & C), and minerals (potassium, magnesium). It can help you to stay hydrated. Here are some times when you cannot have watermelons:
In the late night time too much water can disturb your sleep. It can cause you bloating or vomiting. Try to have watermelons in the morning.
Evening time is not a good time to have watermelons as it contains water and sugar elements that can upset your stomach. Your sleep time can be disturbed.
Watermelon can digest quickly but your meal takes time to digest. Having both can cause gas and discomfort in your body. Try to have it with an empty stomach.
Watermelon can cool your body fast. Having them in winter can make you unwell. In cold weather, your body needs warmth to digest food. You can have them in summer.
In summers watermelons can be light fruit to have, but too much consumption is not good. Its sugar content can cause diabetes and other health problems.