Abstract
An increasing annual rainfall in Japan is statistically discussed. This variation in rainfall was paralleled with hydroelectric potential output data and flood damages in Japan, in the long run. Finally, a relationship between the rainfall and the eleven-year sunspot cycle is tested, although it is concluded the eleven-year sunspot cycle is of little importance. A hypothesis of an inerease trend of water vapour in the atmosphere for a possible cause of the generally warm and rainy years on the world-wide scale is suggested.
