The Tokyo Olympics women's golf tournament could be cut to 54 holes, organisers said Wednesday, because of an approaching tropical storm due to hit Kasumigaseki Country Club at the weekend.

"We have notified the players that we may have to be forced to reduce to a 54-hole competition," International Golf Federation official Heather Daly-Donofrio told a media briefing at the course in Saitama prefecture on Wednesday evening.

"We will not change tomorrow's schedule. We will play 18 holes as scheduled tomorrow. We will play another 18 holes on Friday and then we will continue to track this tropical system and see what Saturday brings."

Daly-Donofrio said the idea of playing extra holes over the next two days to complete four rounds by Friday had been explored, but the extreme heat meant it wasn't feasible.

"The health and safety of our players and caddies is first and foremost," Daly-Donofrio said.

Lexi Thompson's caddie, Jack Fulghum, had to pull out during Wednesday's opening round with heat exhaustion on a day where the thermometers topped 36 Celsius. Similar temperatures are forecast for Thursday and Friday with high humidity seeing the heat index exceed 44C on Wednesday.

"In an ideal world we would make (the cut to 54 holes) before they tee off in their third round, so the players know what they are playing for, but it's all going to depend on that forecast and what we are seeing from our meteorologists.

"We hope the storm veers and goes off and then we can play our final round cleanly on Saturday."

The men's tournament last week was interrupted several times on the opening two days because of heavy rain and dangerous lightning. The second round was not completed until Saturday morning.

The women's tournament is scheduled to finish Saturday but could be extended another day, weather permitting, Daly-Donofrio confirmed, but there is no option to extend past Sunday's Olympics closing ceremony. However, the weather forecast for Sunday is even worse than Saturday.

Sweden's Madelene Sagstrom has a one-shot lead going into Thursday's second round after an opening five-under 66.