We urinate fewer times in summer than in winter and the urine is generally thicker. Explain with reasons.

In summer a large amount of water is lost from the body as sweat, in order to keep the body temperature normal.
To make up for this loss, the kidneys reabsorb more water from the filtrate. As a result less urine is formed, we urinate fewer times, and the urine that is passed is more concentrated or thicker.