Williams doesn't know why it was fast in F1 qualifying at Monza

Lance Stroll was quick throughout the three segments of qualifying to end up fourth fastest while team-mate Felipe Massa was ninth.

Williams has regularly suffered with understeer at low speed, which in turn has hurt it in the rain and on twisty circuits such as Monaco and the Hungaroring.

Williams technical director Paddy Lowe could not explain the turn of speed at Monza and said the team set the car up in expectation for a dry race on Sunday.

"There is a race tomorrow, it's expected to be dry, the race is where you score the points," he said.

"I'm not going to pretend I have any idea why a car is strong or weak in the wet.

"I'm happy we found today the car was strong. It will be very interesting to study that in detail."

Massa said Williams compromised the set-up "very little".

He added: "Maybe some others did the same because if you see the conditions today, it's not only one team that increased the downforce.

"We increase but very little so not really a big compromise. I don't know [why we were quick in the wet]. It's very difficult to get the right explanation.

"The rain today didn't disturb us. To understand 100% why, it's difficult to say."

Stroll will be promoted to second and Massa seventh as a result of grid penalties taken by Max Verstappen and Daniel Ricciardo for engine component changes.

Massa praised Stroll's lap, conceding he simply did not have the pace to beat his team-mate in those conditions.

"Even if I had the perfect lap, it would have been maybe half a second quicker than I was but not Lance's lap time, so he did really a great job today," said Massa.

Stroll becomes the youngest-ever front-row starter in Sunday's race, beating Verstappen by 23 days from last year's Belgian Grand Prix.

"[The] podium at Baku was great, and now starting on the front row here in Monza is great," said Stroll.

"I just put it together there at the end. Throughout the whole session I knew we were competitive, I had an idea where the best grip was under braking and the high-speed corners, Lesmo 1 and 2.

"I just built up to it throughout the sessions, and in Q3 I put it all together and it worked out."