One of the most famous peaks down there, right next to Arthur's Pass in fact, is Avalanche Peak. The name alone says enough about the biggest alpine danger out there.
I visited the area around New Year's a few years ago. It rained hard on the morning of my arrival, late December, and on the slopes just above the pass it was cold enough to turn to snow. Not enough to pose avalanche risk, and it was gone in a few days, but I thought it was a good warning what it could be like out there in winter.
From Avalanche Peak, the glaciers on Mount Rolleston looked great! It looked like a challenging target for an alpine winter climb. I estimate it takes at least three days in winter, from Arthur's Pass and back.Crow Glacier coming down from Mount Rolleston in summertime
Although there are plenty of waterfalls close by, the temperate NZ climate and relatively low altitude of Arthur's Pass mean it's much too warm for them to freeze up, even mid winter (see here
). And you're going to be there late fall. So, your best bet for ice climbing is probably the glaciers coming down into the Crow valley from Mount Rolleston - assuming there isn't too much snow covering them, or causing high avalanche risk from the catchment areas above.Devils Punchbowl Falls in summertime
Finally, don't forget to check out the Arthur's Pass National Parks
site, or drop a line to firstname.lastname@example.org
for more details.