Gives a whole new meaning to the term, the Winds of War.
Apparently, the Japanese hoped to start large forest fires in the Pacific Northwest and Canada with these bombs and spread panic among the civilian population. Because the balloons relied on the jet stream, which lies above the storm track, it was almost guaranteed that the balloon bombs would drop only on forest that were already soaked by rain.
Each balloon required the assembly of 600 strips of rice paper using potato-flour paste, and the work was often done by schoolgirls supervised by paperhangers. Such was the growing issue of hunger in Japan, that the kids had to watched to make sure they weren't eating the paste instead of applying it.
There were plans to use the balloons to drop anthrax. Emperor Hirohito had the sense to nix them.