My intuition tells me that travel guides sometimes focus too much on humidity as the only factor of thermal comfort, forgetting other crucial elements.
The pattern I see, without being able to prove it formally, is a tendency to simplify for the general public, while reality is much more complex.
I've seen summers in Montreal where humidity is high, but shade and a slight breeze make the heat quite bearable.
What would confirm this would be to see more guides include local adaptations or architecture as influencing factors, instead of just humidity figures.