After beating the Sydney Swans in the wet earlier this season, North Melbourne can prepare for a rain-soaked rematch at ANZ Stadium on Friday night.

Rain is forecast in Sydney for the Friday night preliminary final in a scenario that could help the Kangaroos after they held the Swans to their lowest score of the season in the wet in round four.

Key defender Scott Thompson should welcome the forecast after he was the only defender to keep star Swan Lance Franklin goalless when the sides last met.

"At this early stage it looks like there will be a shower or two around in Sydney," Bureau of Meteorology duty forecaster Michael Efron told AFL.com.au.

"There's quite a bit of shower activity expected along the NSW coast and I'd say that would affect the match.

"Thursday evening those showers will pick up from the south and continue into Saturday as well, so they do hang around for a few days.

"There will certainly be some showers around."

Rain is also forecast in Melbourne on Saturday leading into the preliminary final between Hawthorn and Port Adelaide at the MCG.

"There's a chance of some rain during the morning with the risk decreasing in the afternoon and into the evening," Efron said.

"We couldn't rule out something during the game, but it will be much lighter than what we'll see in Sydney."