Until 1999 the holiday was on October 10, but beginning in 2000 it has been changed to the second Monday of the month. The biggest reason was the weather. It had to be just right to accommodate athletes from both warm countries and cold countries. And compared to other cities that had hosted the Games of the Olympiad until then, Tokyo was very rainy. The summer months are hot and humid, moreover, while the weather in spring tends to be very unstable.
Early autumn is the height of the typhoon season and is marked by heavy downpours.
S o the organizers of the Tokyo Games asked meteorologists when would be the best time to hold an outdoor sports event. The answer was mid-October, since by then, the typhoons stop coming, and the skies turn a deep, clear blue. Based on this recommendation, the organizers chose an unusually late date for the Summer Games. Much to the organizers' relief, the Opening Ceremonies were staged under a brilliant, cloudless sky. S ince then Sports Day has generally been blessed with fine weather, and a lot of sporting events are held on this day.