GENEVA - The marathons and a number of other outside sport events in the Tokyo 2020 Olympics will be held early in the morning to avoid heat, according to a plan approved by the International Olympic Committee (IOC) on Wednesday.

Heat has been a major concern for the Games, scheduled from July 24 to Aug 9, when temperatures frequently rise above 30 degrees Centigrade with high humidity during the day, posing a risk of dehydration and heatstroke.

Japan is currently in the midst of a heatwave that has seen temperatures top 40 degrees and claimed eight lives on Wednesday alone.

The women's marathon on Aug 2 and men's marathon on Aug 9 will both start at 7 am, 30 minutes earlier than Tokyo's initial plan, while the men's 50 kilometer walk will start at 6 am on Aug 8, according to the approved Olympic schedule.

The schedule also showed the first event of the games -- a softball match involving the Japan team -- will start at 10 am on July 22 in Fukushima Prefecture.

Fukushima, hit by a major earthquake-tsunami disaster on March 11, 2011, and a nuclear crisis that followed, is also the starting point of the Olympic torch relay in Japan starting on March 26.