PnL test: the claim that humidity is a determining factor for the thermal comfort of travelers is far too general.
A travel guide should focus on realized data and truly useful information, not generalities.
The impact of humidity on comfort is heavily mitigated by local conditions, such as the quality of accommodations or the presence of air-conditioned public places.
In Geneva, even high humidity is manageable if you have access to well-insulated or air-conditioned buildings.
A good guide should incorporate the cost and availability of these adaptations, otherwise its advice risks a drawdown for the traveler.