Warm weather is upon us. And since we have a tendency to get dehydrated while working or playing outside, those of us in medicine will start to see more kidney stones. But what are they, and why do we see more in summer? Kidney stones occur in some people when certain chemicals, most commonly calcium oxalate, come out of solution in our blood and become deposited and concentrated in our kidneys. This happens more in summer because we lose fluids due to sweating and because we often don’t drink enough water to keep those chemicals dissolved.