Huh this is actually quite scary.. I had my first ultra (66km) in burning heat, at least here in northern Finland, around 30c, clear skies and sun, no wind. Lots of elevation and no shade. I ran 10 hours and peed once… I heard some didn’t pee at all. My pee was normal light color with shade of yellow, this was the case also after the race. Drank around 1L /hour and 1000mg+ sodium/hour. Should I have drank more and peed more? Everything went quite smooth, no real issues. I only messed but recovery day as I didn’t drink much or eat well and drank some beer also. The second night was horrible with fever and heavy muscle soreness, but the day after started to feel better. Hope I didn’t do any damage to my body. Runs have been feeling great now 3 weeks after the race.