The Roar's sudden-death semi-final against City at Perry Park on Sunday has been pushed back an hour to 4pm AEST with temperatures forecast to reach 36 degrees.

Polkinghorne says it's nothing out of the ordinary for them, rating the heat and humidity as a major advantage for the locals.

"We're used to it up here. The hotter the better for us," she said on Saturday.

"If we can control the ball and make them chase us a little bit, it'll be even better for us."

City finished fourth this season and won last season's grand final from the same position.

Facing arguably the powerhouse team of the women's competition in a do-or-die contest isn't much of a reward for the Roar, who clinched their third premiership with a 4-1 win over Canberra United on Sunday.

But Brisbane are confident and have every right to be given their record against City this season.

They didn't concede a goal in their two meetings, winning the first 2-0 before a scoreless stalemate three weeks ago.

"That's one thing we've built our season on - our defensive structure and our strength in defence," said Polkinghorne, a 98-cap Matilda.

"Not just the back four but as a whole unit. I think we've done that really well.

"We like to press high and be aggressive and when you've got the likes of (Mackenzie Arnold) behind the back four, it gives you a lot of confidence to make sure you're doing your job."

Polkinghorne said the Roar were intent on wrapping up the double, which they can do in a home grand final - most likely at Perry Park - if they prevail over City.

"It'd be massive. You always want to be winning trophies and to (win both) would be a real testament to the group we've got here and something we'd be really proud of."

Australian Associated Press