The organisers of the rugby World Cup and Formula 1 bosses are monitoring a powerful typhoon forming to the south of Japan which could bring fierce winds and torrential rain over the weekend.
Japan’s Meteorological Agency (JMA) says Typhoon Hagibis is expected to reach the highest level of “violent”.
The JMA added: “It could be the strongest to hit Japan this year.”
World rugby says it is heading in a “north-westerly direction” and could bring disruption to southern Japan.
The typhoon is predicted to hit the southern island of Kyushu on Saturday.
There are two fixtures on the island over the weekend – a potentially crucial match for Ireland against Samoa in Fukuoka on Saturday, while Wales face uruguay in Kumamoto on Sunday.
World Rugby insists it has a “robust contingency plan in place” should the adverse weather impact tournament fixtures.
However, any games cancelled at the World Cup because of the weather are registered as scoreless draws.
Ireland need a bonus-point victory against Samoa to ensure their passage through to the quarter-finals.
Ireland’s defence coach andy farrell said World Rugby is as “keen as we are to get this game played”, adding: “The weather forecast changes all the time anyway, so we won’t probably know until 48 hours out from the game.
“The boys haven’t even spoken about it – we just go from day to day, get on with our preparations.”
Wales might have already sealed their place in the quarter-finals before they face uruguay with victory over Fiji on Wednesday, and head coach warren gatland says he does not want to “waste any negative energy on something that I can’t change”.
“We’ve had some updates in the past from World Rugby about potential weather stuff, and we will deal with that when it comes,” Gatland told BBC Sport.
“We won’t be thinking about that, we will just be focusing on the game.”
In 2014 the race was affected by bad weather, and was halted prematurely when Jules Bianchi crashed heavily, suffering severe head injuries which led to his death nine months later.
BBC weather presenter Ian Fergusson
Super Typhoon Hagibis is looking set to approach western Japan by Saturday. Although the exact track is uncertain and some weakening is expected on reaching Japan, the risk of direct impacts at suzuka this weekend from both rain and wind do look increasingly concerning.