Question

why is more concentrated yellowish urine excreted in summers​

Answer 1

Because in summer season, excessive water is lost in the form of sweat. So, to maintain the water balance in the body, the kidney reabsorbs a large amount of water from the glomerular filtrate. Hence the urine formed is concentrated

Hope it helps

Answer 2

Dark yellow urine indicates concentrated urine and the excretion of waste products in a smaller quantity of water. During summer we sweat more in order to maintain our body temperature. ... If we do not drink sufficient water, then there is greater chance of excreting yellowish urine in summer.