Brisbane Heat 169 for 8 (Kerr 48, G Harris 45, Darlington 3-42) beat Sydney Thunder 125 for 9 (Athapaththu 41, Sippel 3-9, Hancock 2-16) by 44 runs

Heat will play in the Challenger against Perth Scorchers on Wednesday at the WACA. The winner of that match will face Adelaide Strikers in Saturday's final at Adelaide Oval.

"Perth are a quality side and they have got world class players, we're going to have to play well to beat them," Kerr said after getting the player of the match award. "It's about recovering tonight and then getting ready to go again tomorrow."

In good batting conditions, Thunder never seriously challenged in a disappointing ending to a bounce back season after last season's wooden spoon.

"It [surface] definitely bounced a lot...we didn't quite make use of the conditions," Thunder captain Heather Knight said.

Both teams had to endure a cross-country journey after tailing off in the regular season to miss finishing in the top two. Thunder won the toss and elected to field in cool and overcast conditions in a notable change to oppressive recent weather in Perth.

Harris' timing was exquisite, but she also showcased her trademark power by smashing offspinner Lauren Smith into the gigantic sightscreen near the rubble where the Prindiville Stand once stood.

With her half-century in sight, Harris on the next ball attempted another lusty blow but she mistimed to deep midwicket. Harris had dominated the opening stand with Georgia Redmayne, whose struggles this season with being tied down at the crease continued. She made a sluggish 18 off 24 before being caught behind off seamer Hannah Darlington.

Kerr took over with sweet shots around the wicket as Heat eyed a total around 200. She effectively went aerially in the power surge, while Laura Harris was keen to make up for lost time in her second match back after being sidelined for two months with a calf injury.

Harris smashed Smith over deep midwicket for six off her first ball then whacked Darlington on her next delivery with a crunching blow through the off-side.

But she soon fell lbw to a superb full slower delivery from Johnson, who found her length and ignited a late comeback from Thunder. Left-arm spinner Samantha Bates bowled accurately at the death to restrict Heat to a total that only felt par.

But the dismissal seemed to ignite Athapaththu, who went after left-arm spinner Jess Jonassen with decisive footwork. She was less assured against pace and it proved her downfall on 41 when Athapaththu succumbed to a well-targeted delivery from Sippel.

When Kerr had Phoebe Litchfield caught and bowled, Thunder slumped to 61 for 3 at the halfway point and they never recovered as Heat lived to fight another day.