Sumatra in octobre?

Does it make sense to go to Sumatra in octobre, or should we go to Sulawesi
instead, because of the rain season?
We'd like to go from the North (Medan) to the south, taking about 4 weeks.
We'd like to hike in jungle and see some wildlife (we know what it is to
walk in the jungle). Maybe do some climbing.

What's the rainseason like: whole days of rain, or just the odd shower at
the end of the day?

Does anbody know how Gunung Leuser is, after the flooding?

Can we visit Blankejeren in Aceh, safely?

Any tips?
Paul.