My brother has trekked over through of the most demanding areas; the Himalyas in Nepal, the glacier fields of Pakistan, and the
Andes of South America. There aren't tourist hikes, but treks of anywhere from three to six weeks in duration. Depending on elevations at the moment he would encounter dry heat, rain, or heavy snows. He, and other experienced trekkers, use Nikwax, as they feel it offers the best combination of protection and breathability.
Good enough for my in my much more limited applications.
