It began several hours ago, and with the race around ninety minutes away it continues.

"It's cold, grey and damp," tweet McLaren, "rain, rain, rain," echoes Renault.

While a couple of races earlier in the season were predicted to be hit by rain, it finally looks as though the forecasters have got it right, as the Circuit Gilles Villeneuve continues to be lashed by showers. What started as light drizzle a couple of hours back continues to increase in intensity, it looks like we're in for a soggy afternoon.

Consequently, the form book looks to be heading out of the window, and we finally get to see how well the Pirellis work in the wet.

Paul Hembery is confident, and while Pirelli hasn't yet had a proper wet race it has tested in the wet on several occasions and there was one wet session in Turkey last month. That said, a number of drivers, including Jenson Button, have never run on the Italian rubber in the wet, the Englishman opting not to run because he wanted to save his wet tyres for the remainder of the weekend in case the weather didn't let up. Similarly, teammate Lewis Hamilton only ran a few wet laps during one of the Barcelona tests.

With the experts predicting a 60 percent chance of rain today, McLaren is the most high profile team believed to have sacrificed its qualifying bid in an attempt to be ready should they be proved right, though Button denied this. Renault also is said to have prepared for a wet race.

With McLaren widely thought to be the favourites going into this weekend, such a move might explain the Woking team's relatively poor performance yesterday afternoon.

An hour before the race is due to get underway, Bob Constanduros emails to say that Alguersuari is to start from the pitlane as the front torsion bars, upper rear wing flap and lower rear wing gurney have been changed on his car and they are different from the ones originally used. Changes have also been made to the set up of the suspension. All this is anticipation of it remaining very wet this afternoon, the Spaniard looking to emulate something of the performance of Sebastian Vettel at Monza in 2008.

Worth noting that Renault have changed the engine in Heidfeld's car but without penalty.

Even in the dry there have been incidents aplenty this weekend with Vettel hitting the Champions' Wall on Friday morning and Adrian Sutil, Kamui Kobayashi and Jerome d'Ambrosio all crashing in the afternoon.

Complaining of feeling unwell after the Friday morning session, Sergio Perez, who crashed heavily in Monaco, has been replaced by Pedro de la Rosa.

Five minutes before the pitlane opens it stops raining. Mike Gascoyne claims that there won't be any further rain for a while however, the high humidity means the track won't dry out very quickly. There are already numerous parts of the track with standing water and it almost certain that the start will be on intermediates or wets. There is also talk of starting behind the Safety Car.

With so little experience of such conditions nobody is in a hurry to take their place on the grid, instead driver return to the pits in order to try practice starts and evaluate the tyres.

Lotus' weather people (Meteo France) claim there won't be any further rain for the first thirty minutes of the race.

One of the last onto the grid is Rosberg, the Mercedes driver running full wets. The German makes it onto the grid by the skin of his teeth. Ross Brawn says that both of his drivers will start the race on full wets with "no chance" of starting on inters. Heidfeld complains that grip is "incredibly low".

Five minutes before the start, the air temperature is 19 degrees C, while the track temperature is 20 degrees.

Sadly, the officials announce that the race will start behind the Safety Car. In the pitlane, McLaren team members are using blowers to dry their particular bit of tarmac. Because we're starting behind the Safety Car it means that everyone must start on full wets and DRS is disabled until Race Control decides otherwise. It also means the race is underway the moment the Safety Car leaves the grid.

As the field heads off, Schumacher is advised that no further rain is expected until fifteen minutes into the race. Onboard footage from Hamilton's car shows just how poor the visibility is.

Massa is told that "reasonably heavy" rain is expected in fifteen to twenty minutes.

It's noticeable that some cars are running a lot more wing than others.