When spring starts in March, winter pressure patterns such as "the high-pressure area to the west, and the low-pressure area to the east" become unstable.
Weather periodically changes as a cycle of three cold and clear days and four warm and rainy days.
From the end of March to the beginning of April, rainy days usually continue, so called "Natane Tsuyu".
Also, from the middle of June to the middle of July is the rainy season, except in Hokkaido.
From the end of April to the beginning of May, Japan celebrates what is called "Golden Week".
In this week, there are a few national holidays; on April 29th, May 3rd, 4th and 5th.
Many Japanese travel during this holiday period, so trains are full and highways are heavily crowded.
Room rates at hotels are also increased at this time and become very expensive.
It would not be recommended for tourists from other countries to travel to Japan during this week.
However, after Golden Week, fine weather continues and site seeing places are not crowded.
You can also enjoy seeing beautiful rice fields. It is good season to travel in Japan.