Rain certainly shakes things up. While Sebastian Vettel on his 39th Grand Prix pole and Lewis Hamilton lining up alongside him on the front row were arguably within expectations for the Canadian Grand Prix, it's hard to see how anyone would have put money on a second row start for the Williams F1 of Valtteri Bottas. Meanwhile neither McLaren made it through to Q3, after a red flag for a early exit into the tyre wall by a Ferrari.

The start of qualifying saw the start of a new light rain shower hitting the Circuit Gilles Villeneuve, as the unseasonably cold and dismal conditions in Montreal persisted into Saturday afternoon. The good news was that the teams were confident that the rain would be short-lived, but that simply meant that getting through to Q2 was going to be more of a lottery than usual and a factor of being out at precisely the right moment when the conditions were at their optimum.

No surprise then that there was a flood of cars taking to the track the minute the session went green, everyone hoping that the track was still dry enough to run on the supersoft dry tyres for one quick lap before conditions deteriorate. Unfortunately that wasn't the case, and after a perilous initial reconnaissance lap the cars all streamed straight back onto pit lane for an emergency change to intermediates - the last thing the teams wanted given the supply of just four sets all the teams have available to them for the entire weekend - and with the forecast of showers looking more likely for race day.

After the phoney start on the slicks, Toro Rosso's Jean-Eric Vergne set the first flying lap on the intermediates with a time of 1:28.204s that was quickly beaten by Felipe Massa and then emphatically sliced by over a second to 1:26.781s by Nico Rosberg as the cars started to forge a dry line on the circuit. Even so, the teams were advising their drivers that they expected times to drop by more than two seconds from here provided the rain didn't worsen.

A few scary moments for Adrian Sutil, Lewis Hamilton and Fernando Alonso underlined just how tricky these crossover conditions were for the drivers as they continued to push to the limit of their tyres' adhesion and their own level of talent, and ensuring that despite a completely dry line in some parts of the track there was no realistic chance of the drivers trying slicks again anytime soon.

Red Bull's Sebastian Vettel proved the pit wall prophecies right by calmly setting a new benchmark of 1:24.788s at the midway point which he lowered by seven-tenths next time round in response to an improved effort by Lewis Hamilton in the Mercedes. Vettel ran wide on his next lap indicating that his current intermediates had reach the end of life status and that a visit to pit lane was mandated, allowing Nico Rosberg to move to the top of the timesheets with a new target time of 1:23.840s swiftly bettered by a tenth by Felipe massa in the Ferrari.

Under pressure with time running out was Jenson Button, firmly in the drop zone and complaining about being blocked by Vettel; seconds later, and starkly showing how rapidly things were changing in this all-action Q1 session, he was up to fifth but then rapidly shuffled down to ninth by the cars following him across the line. It could all have gone very wrong for the McLaren driver after that, but a brief pick-up in the rain prevented many of those still on flying laps from doing the business and improving their times in the last seconds.

When the dust - or rather, the water spray - had finally settled after the chequered flag called time on the first part of qualifying, there were two big surprises left without a seat in Q2. For the second time in succession, Force India's Paul di Resta was left on the wrong side of the cut, a gearbox glitch leaving him just over a tenth off the back of Toro Rosso's Daniel Ricciardo. That meant di Resta is now faced with having to claw his way back up from 17th place on the grid on Sunday. The Scot was joined in the elimination zone by Lotus F1's Romain Grosjean, who will now start from last place after finishing 19th in the times and then having his ten-place grid penalty from Monaco to serve. Alongside di Resta and Grosjean on the sidelines for the rest of qualifying were the usual suspects of Charles Pic, Jule Bianchi, Mac Chilton and Giedo van der Garde

Webber, Rosberg, Hamilton and Toro Rosso's Jean-Eric Vergne were quick to take to the track as race control declared "a change in climatic conditions" - and not in a good way, a surge in the rain front having wiped out the previously emerging dry line. That put the times back around the 90-second mark, with Hamilton's first flier clocking in at 1m29.259s before a close encounter with the wall of champions; other drivers including Fernando Alonso and Sebastian Vettel started overshooting the final chicane as the rain really started to set in. It was growing so bad that Sergio Perez was even told by the McLaren pit wall that there was a serious team discussion about whether the full wet would be shortly be required.

As quickly as it had waxed, the rain started to wane again and Vettel managed a cleaner lap to go top with a time of 1:28.825s that was soon improved to 1:28.825s by his team mate Mark Webber, although turn 3 was still bad enough to claim both Adrian Sutil and Lewis Hamilton for a synchronised run down the escape road. A couple of minutes later and there was a much more emphatic mishap at the same spot, this time for Felipe Massa who locked the rears into the right-hander and slid sideways off the track, over the sodden grass and sideways into the tyre barrier. Although it didn't look like a hard hit he was still hustled off to the medical centre for a checkover.

It was the end of the session for Massa, and a temporary hiatus for everyone else as the race stewards quickly threw a red flag to stop the clock at just shy of two seconds - enough to get out for one more flying lap, a slender lifeline for those currently in the 'drop zone' - Pastor Maldonado, Jenson Button, Daniel Ricciardo, Esteban Guti?rrez and Adrian Sutil. The ensuing stampede from the queue at the pit lane exit at the restart looked more like a full-blown Grand Prix grid start and there were solid laps from Ricciardo and Sutil to push themselves into the top ten and make it into Q3 at the expense of Nico Hulkenberg and Sergio Perez; most upset of all was Perez' team mate Jenson Button, who failed to get across the start/finish line before the chequered flag came out and was therefore unable to try improving his existing time, leaving him mired in 14th place on the grid for Sunday's race.

In the meantime Lewis Hamilton had put in a late flier to take the Q2 honours for Mercedes with a lap of 1:27.649, and there were hopes that this indicated improving conditions for the final ten-minute part of what had so far been a wet, wild and occasionally downright wacky qualifying. With more rain in sight approaching from over the city skyline, there was no delay by the remaining ten cars in taking to the track - Kimi Raikkonen even cheekily dodging around Mark Webber in the queue waiting to exit the pit lane when the lights went green.

The first flurry of flying laps saw Vettel go top with a time of 1:25.425s half a tenth ahead of Hamilton with Rosberg, Alonso and Raikkonen next up. Webber improved to fourth place after running wide on his first attempt, and then Valtteri Bottas - arguably the real surprise name in the Q3 line-up - proved he more than deserved his spot by popping up into third place to split the two Mercedes, the Finn clearly loving the treacherous conditions.

Just over halfway through Q3 and the increasing rain especially in the final sector had all-but frozen the grid order, meaning that there were no further improvements: Vettel and Hamilton will start from the front while Bottas will be joined by Rosberg on row 2, leaving a nervous Mark Webber staring at the unfamiliar sight of the rear-end of a Williams for the start of Sunday's race.

Next to Webber in sixth place on the grid will be Fernando Alonso, acutely aware of the risks he faces from first lap collisions and the damage they can do to his title campaign. Rounding out the top ten are Jean-Eric Vergne impressively managing seventh place alongside Adrian Sutil, while his Toro Rosso team mate Daniel Ricciardo will start from tenth with Kimi Raikkonen just ahead and to the side of him.

That should certainly make for an interesting start to Sunday's racing action.

Full qualifying times are available.