The Blaze has become the first side to qualify for the finals after posting its seventh consecutive win.
It beat the Central Hinds by five wickets at Pukekura Park on Saturday to cement its spot at the top of the standings.
The Hinds were restricted to 123 for six despite a punchy 70 from 45 balls from Jess Watkin.
Jess Kerr led the bowling effort with an outstanding four for 18. She also chipped in with 25 not out from 15 balls to seal the win.
The Blaze (28 points) will probably be joined in the playoffs by the Otago Sparks (24), while Auckland and Canterbury (both 12) seemed destined to battle it out for the remaining spot.
The Hinds and the Northern Brave both have four points.
The men’s competition is more evenly balanced.
Canterbury (20 points), Northern (18) and Wellington (16) occupy the top three spots, but Central and Auckland (both 12) remain in the race.
Otago (six) is out of contention in last place, but the Volts can claim a glory of sorts by association.
Former Otago batter Michael Bracewell smashed his way into the record books and helped lift the Firebirds to third with a staggering innings.
He swatted 141 not out from just 65 balls to almost single-handedly sink Central at Pukekura Park on Saturday.
The Stags posted 227 for four and had reduced the visiting side to 43 for five.
But Bracewell pummelled 11 sixes and 11 boundaries in one of the great twenty20 knocks.
It was his maiden century in the format and the highest T20 score posted in New Zealand.
The well-built 30-year-old has always possessed power, and the undersized boundaries at the venue were barely a challenge.
But you still have to hit the ball somewhere near the middle of the bat, and he certainly managed that.
Bracewell attempted to play down his historic knock soon after the game, telling Spark Sport with a straight face that it took a "team effort" to record the phenomenal win.
"Coming in, we knew it was going to be a good wicket, and CD certainly showed that with the bat," he said.
"We kept losing wickets at the top and through the middle, so we just tried to take the game deep, and it's amazing what happens when you just believe.
"You're always looking to go out there and just play positive, and it's a really conducive run-scoring field out there — fast outfield and short boundaries — so we kept up with the rate. And you've just got to try back yourself and take runs at the back end."
Bracewell, who played for New Zealand at under-19 level, started off as a wicketkeeper.
The left-hander made his debut for Otago in 2011 as a top-order batter.
He made steady progress, and in the 2013-14 season scored four first-class centuries.
It got him noticed by the national selectors, but he struggled to maintain that form and moved to Wellington for a refresh in 2017-18.
His leadership potential was immediately recognised, and he was appointed captain of the first-class team.
He also worked on his right-arm offspin and, in recent seasons, has developed the skill to a point where he can claim all-rounder status.
Bracewell is one of three former Otago players in the Firebirds line-up.
Talented all-rounder Nathan Smith transferred to Wellington this season, and Black Cap Jimmy Neesham made the move in 2018-19.
Former Otago A player Ollie Newton moved there for work but his cricket career has really flourished.
