Many of the 80 men’s and 57 women’s Olympic skiff sailing teams arrived weeks ago to practice for the most important event on the calendar, only for the first two days of qualifying to be completely held up.

"We’ve had some really frustrating conditions here, not just with unstable and patchy air, but also with seriously thick fog," said principal race officer David Campbell-James.

"We worked hard to try to set courses yesterday but it was just never possible.

 "We may get something to play with later this afternoon, but it appears we may have to wait another day before we see any quality racing."

The Worlds schedule is likely to be compressed, with the qualifying rounds extended into Thursday (August 31).

Gold fleet would also extend to have four races on Friday (September 1) and then more racing Saturday morning, with only the top 10 boats competing in the Final on Saturday afternoon.

Campbell-James is optimistic for good conditions at the end of the week.

"With Porto opening up the new Ocean Terminal and inner harbour to the 49er fleet, we’ve got a ten-story viewing platform looking directly down on the race course," he added.

"With the wind likely to come in by then, it could be the best medal racing we have ever had in the class."

Men’s skiff racing, in the 49er Class, became a part of the Olympics at Sydney in 2000.

Women’s skiff racing, in the 49erFX Class, made its Olympic debut at Rio 2016.