If we go sometime during the end of March or beginning of April, we will have the chance to see the cherry blossoms in bloom! It's a popular time of year to partake in Hanami, or flower viewing. Here, I shall let Danny Choo explain with his beautiful photographs (except for his creepy anime doll he takes everywhere):
http://www.dannychoo.com/post/en/1690/Tokyo+Cherry+Blossom.html