Koalas stay in their eucalyptus trees. Their thick fur is partially waterproof, although it does not protect them in a particularly heavy downpour.
Koalas only go though a stage of dormancy or hibernation during their embryo state. In adulthood Koalas do no hibernate.
Where do flies go when it rains
If you go outside when it rains you better take an umbrella.
Claude Rains went by 'Willy Wains'.
Koalas regularly go on the ground. Koalas do not spend their entire lives in a single tree. They have a home range which may extend up to a kilometre squared in size, so they need to go on the ground in order to move between their home trees.
Mole holes
Adult koalas are simply called koalas.
Koalas are not primates. Koalas are marsupials.
When it rains in middle of day camp, you need to go indoors and do indoor activities.
Koalas are mammals, and most mammals have skin, either with or without fur or hair. In the case of the koala, the fur has particular functions. The koala's fur helps to keep it cool in summer and warm in winter. Its outer layer is partially waterproof, so that when rains do come, the koala does not become saturated.
A counterexample for "when it rains it pours" could be a situation where it rains lightly throughout the day without escalating into a heavy downpour. This would go against the idea that once it starts raining, it will intensify significantly.
There are no koalas in Germany. Koalas are endemic to eastern Australia.