No foundation at all for a typical GA aircraft, if my distant memory of chemistry is correct.
Let's suppose you park your wonderplane with 100 Litres of empty capacity in its tank, on a summer day when the temperature is 30C. Overnight it cools to 10C.
At 30°C, 3.04 grams of water can be held in a 100 litre volume, and at 10°C that falls to 0.94 grams. So, worst case scenario, if the relative humidity is 100%, you could have 2.1 cc of water at the bottom of your tank if all the water vapour condenses onto the surface of the fuel tank and you refuel to the brim while the temperature is still cold.
There would actually be a bit less water than that at the bottom of your tank, as some water can be dissolved in Avgas - I don’t know how much. As your fuel cooled at high altitude, more water could come out of solution.
I don’t know if the saturated vapour density of water will be affected by the presence of other gasses in your fuel tank; we need someone who’s been a scientist more recently than me! If there is an effect, I would anticipate it would be a reduction in the amount of water held.
Conclusion: if your engine fails due to water contamination, it’s not likely to be because water condensed overnight in your fuel tank.