A tropical storm is forecast to hit Tokyo on the last day of the Olympic Games, organisers said on Friday, but did not announce any changes in the schedule.
Japan's weather agency predicted strong winds, high waves and the risk of landslides and floods along the eastern coast from Saturday afternoon to Sunday, when Tropical Storm Mirinae is expected to pass over the capital.
The Olympics' closing ceremony is on Sunday evening, with medal events including water polo and rhythmic gymnastics taking place at indoor venues in the city during the day.
Cycling track races are also scheduled in Shizuoka, south-west of Tokyo, while the men's marathon will kick off early on Sunday in the far northern city of Sapporo.
"We are firmly and calmly paying attention" to the path of the storm, Tokyo 2020 organising committee spokesman Masa Takaya said.
"It is necessary to inform you objectively, so that we can avoid excessive overreaction," he said.
A storm hit Japan last week, forcing Games organisers to reschedule some rowing and archery events, although they brought forward the surfing finals to take advantage of powerful waves.
On Friday, Mirinae was about 100 kilometres north of Minamidaito island, near the southern archipelago of Okinawa.
It was moving east, with gusts of up to 108 kilometres per hour.
Another tropical storm is hovering in the Taiwan Strait, moving towards Japan.
Japan's typhoon season runs from about May to October, peaking in August and September.
In 2019, Typhoon Hagibis smashed into Japan as it hosted the Rugby World Cup, killing more than 100 people.
Meanwhile, Covid-19 case numbers continue to rise in Japan, with the country deciding this week to expand Covid-19 curbs to more than 70 per cent of its population. In contrast to the stringent lockdowns in some countries, authorities are relying mainly on requests for self-restraint and peer pressure.
With nationwide new cases topping 15,000 a day for the first time this week, expectations are that Prime Minister Yoshihide Suga may declare a nationwide state of emergency, although he said on Thursday he was not considering this now.
Some ruling legislators suggested legal changes to allow stricter enforcement of curbs, but any move to a western-style lockdown would be controversial and take time.