I recently got this game and have been really enjoying the solo play.
I think I am close to mastering the easiest level - easy mountain, easy weather. The key has been the judicious use of the risk tokens.
I "burn" the risk tokens off the acclimatization level of a climber slowly moving forward at the base of the mountain (and getting the +1 acclimatization per turn), while the other climber races to pitch a tent just below the 8,000 foot mark on the left side and hunkers down waiting for the right combination of cards to summit and drop back down to the tent. Meanwhile, the other climber slowly progresses up the mountain. My goal is to get the second climber to summit on the last turn by "leapfrogging" over the camped first climber, using the combination of 3/3/2 movement cards and one of the 0 risk tokens that I save one for the end. This is more difficult to pull off with the winter weather.
After playing with the winter weather or the hard side of the mountain, my game play has definitely improved. I have not yet played with both the winter weather and hard side of the mountain.
I have done my solo plays (around 10 of them) all on the winter board with bad weather. So far, my strategy has been to fully prep one guy and let the other guy walk up slowly with any remaining points (for example, when a risk token eats up more points than I was hoping for). So far, I only get to 11-13 points at most, getting one climber at 8 points at most. I have tried the strategy of getting to 10 acclamitisation asap with one guy and running up to the peak as quickly as possible, but my guy always died, even if I made him descent from the peak and hide in his tent at the 8 point mark.