Hi Steve - I agree with the weather. This will be our 4th trip in October and only once did we not make it to the summit due to weather in early/mid-October. The one time we didn't make it was our first time in October when we didn't bring crampons or an ice ax and only had micro-spikes. It got a little sketchy above TC, so we turned around. Ever since, if there has been snow or planning to be snow during our trip, we bring the appropriate gear and always put safety above the summit.
We don't mind the darkness nor the cold. It's great training for us as we are looking to climb in Peru next May/June.
