Rookie Robert Wickens has taken the first pole of the new IndyCar season while defending champion Josef Newgarden did not advance from the first round of qualifying.
The Canadian will share the front row with Will Power, while Newgarden qualified in 13th.
In a Firestone Fast 6 marked by enough rain to make conditions tricky, but still not enough for wets, Wickens stunned by taking the #6 Schmidt Peterson Honda to the top of the timesheets at the very last moment.
He bumped Power (#12 Team Penske Chevrolet) off pole, while two more rookies in Matheus Leist (#4 AJ Foyt Chevrolet) and Jordan King (#20 Ed Carpenter Chevrolet) will start off Row 2.
Takuma Sato (#30 Rahal Letterman Lanigan Honda) qualified fifth and Ryan Hunter-Reay (#28 Andretti Autosport Honda) sixth.
Scott Dixon was caught out by the rain during the second round of qualifying, waiting too long to attempt a serious flyer and ending up ninth on the grid in the #9 Chip Ganassi Honda.
Simon Pagenaud was one of many to encounter trouble at Turn 1 in the final minutes of the same session, twice running the #22 Team Penske Chevrolet off then half-spinning the next time around and bringing out the red flag in the final minute.
The 2016 champion lost his best two laps and will start 11th.
Alexander Rossi (#27 Andretti Autosport Honda) will also be on the sixth row for the start after a penalty for qualifying interference which cost him a place in the Fast 6.
Newgarden (#1 Team Penske Chevrolet) and 2017 St Petersburg winner Sebastien Bourdais (#18 DCR w/ Vasser-Sullivan Honda) qualified on the seventh row.
Marco Andretti (#98 Andretti Herta w/ Curb-Agajanian Honda) missed out on the second round, also due to qualifying interference, and will take up 18th position on the starting grid.
Graham Rahal makes up the very rear of the 24-car field having spun the #15 Rahal Letterman Lanigan Honda at Turn 10.
The 110-lap Firestone Grand Prix of St Petersburg starts tomorrow at 0340 AEDT.
Starting grid: St Petersburg
|1||6||Robert Wickens (R)||D/H/F||1:01.6643||Fast Six|
|2||12||Will Power||D/C/F||1:01.7346||Fast Six|
|3||4||Matheus Leist (R)||D/C/F||1:01.7631||Fast Six|
|4||20||Jordan King (R)||D/C/F||1:01.7633||Fast Six|
|5||30||Takuma Sato||D/H/F||1:01.8821||Fast Six|
|6||28||Ryan Hunter-Reay||D/H/F||1:02.0385||Fast Six|
|7||5||James Hinchcliffe||D/H/F||1:00.9986||Round 2/Top 12|
|8||88||Gabby Chaves||D/C/F||1:01.1191||Round 2/Top 12|
|9||9||Scott Dixon||D/H/F||1:01.6527||Round 2/Top 12|
|10||14||Tony Kanaan||D/C/F||1:01.7213||Round 2/Top 12|
|11||22||Simon Pagenaud||D/C/F||1:04.6739||Round 2/Top 12|
|12||27||Alexander Rossi||D/H/F||1:07.0377||Round 2/Top 12|
|13||1||Josef Newgarden||D/C/F||1:00.4320||Round 1/Group 1|
|14||18||Sebastien Bourdais||D/H/F||1:00.9587||Round 1/Group 2|
|15||26||Zach Veach (R)||D/H/F||1:00.4585||Round 1/Group 1|
|16||21||Spencer Pigot||D/C/F||1:00.9668||Round 1/Group 2|
|17||10||Ed Jones||D/H/F||1:00.5009||Round 1/Group 1|
|18||98||Marco Andretti||D/H/F||1:01.3013||Round 1/Group 2|
|19||60||Jack Harvey (R)||D/H/F||1:01.0270||Round 1/Group 1|
|20||59||Max Chilton||D/C/F||1:01.3360||Round 1/Group 2|
|21||23||Charlie Kimball||D/C/F||1:01.1868||Round 1/Group 1|
|22||19||Zachary Claman DeMelo (R)||D/H/F||1:01.8567||Round 1/Group 2|
|23||32||Rene Binder (R)||D/C/F||1:01.7003||Round 1/Group 1|
|24||15||Graham Rahal||D/H/F||1:04.0990||Round 1/Group 2|
(C)hassis: D=Dallara | (E)ngine: C=Chevy, H=Honda | (T)yre: F=Firestone