Why fast change becomes dangerous
Sweat, rain, wind, and a long descent can cause rapid cooling. Lightning makes exposed ridges hazardous. Fog or cloud can reduce visibility. Wet roads and trails change traction.
When to abandon the plan
Turn around when weather is approaching faster than expected, thunder is heard near exposed terrain, visibility is deteriorating, or the group no longer has the layers, daylight, or transportation margin needed for a safe return.