Weather in the Yatil Mountains

The players in my D&D campaign will soon be headed into the Yatil Mountains in search of the lost treasure hoard of the Archmage Iggwilv (see module S4: The Lost Caverns of Tsojcanth ). An adventure set among high mountain passes really calls out for guidelines for handling weather and temperature, which the published module doesn't speak to at all (except for the perfunctory inclusion of…