Verified Answer :

gelatine1

on a sunny day the temperature might be above 40°C which will cause the water to vaporize quicker as if it were cloudy and colder


    I would tend to think that the amount of sunlight reaching the water is irrelevant.

The color of the surface that the water lies on is more important.  A black, matte

surface absorbs more infrared radiation than a light-colored, reflective surface.