The endurance events have been moved to the "cooler conditions" of northern Japan.
The International Olympic Committee (IOC) has announced that it plans to move next year's Olympic marathon and race walking events to the "cooler conditions" of Sapporo.
The host city for the 1972 Winter Olympics, Sapporo is more than 800km north of Tokyo on the northern Japanese island of Hokkaido.
The IOC said the move was "part of comprehensive measures to protect athletes, officials and spectators".
Sapporo's temperatures during the Games period are said to be around five to six degrees centigrade cooler during the day than in Tokyo.
The proposal comes after 28 competitors pulled out during the women's marathon at Doha 2019, which started at midnight with 68 runners.
World Athletics have been informed about the proposed Tokyo 2020 changes after the IOC Working Group identified the events would put "particular heat stress on the athletes".
IOC President Thomas Bach said: “Athletes’ health and well-being are always at the heart of our concerns. A range of measures to protect the athletes have already been announced.
"The new far-reaching proposals to move the marathon and race walking events show how seriously we take such concerns.
"The Olympic Games are the platform where athletes can give ‘once-in-a-lifetime’ performances, and these measures ensure they have the conditions to give their best. I would like to thank World Athletics, and we look forward to working with them on the implementation.”
World Athletics President Sebastian Coe added: "We have been working closely with the IOC and Tokyo 2020 on the potential weather conditions at next year’s Olympic Games and will continue to work with the IOC and Tokyo 2020 on the proposal to move the road events to Sapporo.
"Giving athletes the best platform for their performances within the environment they are in is central to all major events, and we will work with the organisers to create the very best marathon and race walk courses for next year’s Olympic Games.”
The planned move is part of a wide range of measures to mitigate the effects of the temperatures which may occur next summer.
Other heat countermeasures planned for Tokyo 2020 include putting the 5000m and longer distance races in the evening athletics sessions.
Meanwhile, morning rugby games are set to finish by midday, and the mountain bike start time has been delayed to 3pm.
23 Jul - 8 Aug 2021
Tokyo 2020 | Olympic Games