It isn't gonna be the same each year but last year snow came abit early and it did snow when I was there in mid-3rd week of dec in Kyoto, Nara, Hiroshima/Miyajima. But it's not like it will snow for the entire day. It is on and off, and light snow.Does it snow in Kansai area ( Osaka, Kyoto, Kobe, Hiroshima) in mid Dec?