The third hour-long practice session at Edmonton City Center Airport got underway at 9am local time under overcast skies: while there was no falling rain by the time that the session went green, there had been a storm overnight that had washed yesterday's rubber off the 2.24-mile, 13-turn temporary circuit built on the airport runways, making the conditions even trickier than they had been on Friday.
Josef Newgarden got into problems early on the drying track, with a ride through the wet infield area grass at turn 11 to bring out a first red flag within ten minutes of the start of the session. When proceedings resumed, Scott Dixon went top with a lap of 1:19.4532s, but then Ryan Hunter-Reay promptly went a third of a second faster to head the timesheets.
Just before the 20 minute mark, Helio Castroneves brought out a brief second red flag to have his car re-fired following a spin in the ever-tricky turn 1 that had also caught him out on Friday afternoon.
The session quickly resumed and the track conditions were rapidly improving, allowing Will Power to go top of the times with a new benchmark lap of 1:18.3880s ahead of his Penske team mate Ryan Briscoe. However, close-call scares for JR Hildebrand, Oriol Servia and Will Power demonstrated how easy it still was to get caught out.
Alex Tagliani made a leap to the top 25 minutes in with a lap of 1:17.6158s and Mike Conway continued to craft a good weekend by promptly claiming second spot a quarter of a second back and Takuma Sato, Simon Pagenaud, James Hinchcliffe and Sebastien Bourdais also coming on strong before Will Power put them all in their place with a new top time of 1:17.5764s at the midpoint of the session, albeit someway off the best times seen on Friday.
Second later, Justin Wilson was the trigger for a quick third red flag after spinning and stalling at the final corner. His Dale Coyne Racing team mate also went on sight-seeing excursion once track activity resumed, but he did so without stalling which meant there was no red flag required. Charlie Kimball similarly took a stroll through the grass at turn 12 without causing a red flag after he just succeeded in keeping the #83 off the wall.
As the session dipped into the final ten minutes, still no one had managed to unseat Will Power from the top of the timesheets although Tagliani had improved to just 0.0078s back and Dixon only half a tenth of a second further back in third. But finally it was Takuma Sato who did the honours, going top with a lap of 1:17.4537s with five minutes remaining.
Power didn't much like that and reasserted his claim to the top with a lap of 1:17.2247s, only to have Sato fight back with a effort of 1:17.1308s and then Scott Dixon mugging them both with the first lap of the day in the 1:16s, proving that the conditions were finally getting back close to where the drivers had left them at the end of Friday.
Dario Franchitti took his team mate's hint and went top next lap around with a lap of 1:16.8904s, in a sequence that looked like a genuine dress rehersal of the qualifying sesson to come later in the day. Power, Wilson and Tagliani all improved their times late in the session to bump a pit-bound Sato down to sixth by the time the chequered flag, but no one had any response for the Ganassi duo at the top before the session ended.