We will spend a day in Helsinki in the beginning of December. (As we do most years cruising from Stockholm.) What temporary exhibitions are available in Helsinki's museum or elsewhere at that time?
A couple of pointers:
Tennispalatsi (Helsinki Art Museum)
There will be two ongoing exhibitions in December:
Tip: free entrace to Tennispalatsi on Fridays :)
If you're after something decidedly Finnish, you should probably check out the Gallen-Kallela one.
Kiasma (modern art)
See their calendar
Ateneum (Finnish National Gallery)
They'll have (among others) these temporary exhibitions:
...plus permanent collections.
All of the above are in located in the heart of the city. If you're willing to venture out to the suburbs, there's e.g. EMMA (Espoo Museum of Modern Art) ~half hour bus trip away, with exhibitions like:
Of course, there are lots of other places too. For example, you'll find info on smaller, City of Helsinki owned museums here. I was actually going to mention, as one example, the same exhibition as Mark did: Out to Sea – 150 Years of Sailing in Helsinki at Hakasalmi Villa, next to Finlandia Hall.
Helsinki City Museum has the 'Out to Sea' exhibit until January, which celebrates 150 years of Sailing in Helsinki: