In hot weather, people experience a special condition. It is not an illness but they become tired and they lose appetite and like to drink a lot of water. What is the name of this condition?
Sometimes people become "listless" in very hot weather.
Heatstroke? Sunstroke? Dehydration?
Any of those can make you quite ill. I had heatstroke once because I fell asleep in the sun at midday and woke up at 4pm. I was very sick (vomiting) and felt very tired for the rest of the day. I was also clearly very dehydrated and drank about four litres of water in the next couple of hours.