Climbing outer layers do depend on the conditions, though I normally have the same mid-layer of an Icarus Flight Jacket (Women's Phoenix Flight). Its PrimaLoft® ThermoPlume synthetic insulation with THERMO STRETCH PRO fleece panels give a really good balance of warmth and flexibility. Plus it’s got the long back which helps eliminate cold spots and the hood which means you don’t need to pack an (extra weight) hat of any.