I have been asked quite a lot recently about the effect of sunshine on thermography.
Strong sunlight will cause solar loading, this means that the sun will heat the objects that it is shining on. While we don’t normally worry about colour in thermography, colour will strongly affect the amount of heat transfer that takes place in the visible portion of the spectrum, so dark colours will absorb more of the visible light than light colours. The heating may affect the ability to detect faults.
For thermography in strong sunshine, it is best to avoid working during the hours of sunlight, and better to leave this type of survey until night-time. If you suspect that the sun may be affecting the objects that you are surveying, and then survey them at night.