Felipe Massa says Williams is keeping an eye on the threat of rain for this Sunday's German Grand Prix at Hockenheim.
While the area was bathed in sunshine and temperatures of up to 33c during Friday practice, forecasts suggest that cooler conditions on Sunday could bring with it a threat of rain.
"We have had a good day today" he said after finishing the session in sixth place.
"We have done a lot of work on the set-up especially after the suspension changes we have had to make. I hope we can carry on the improvements throughout the weekend.
"We made a good step-up between the first and second sessions which is good. We will have to be cautious about the rain on Sunday and we will be thinking ahead with a view to prepare the car for that."
Team-mate Valtteri Bottas, who handed over his car to development driver Susie Wolff for the first session, rounded out the top 10.
"The track was very hot today which affected the tyres a lot," he said.
"It wasn't easy on the Super Soft on the long runs and that's a point we have highlighted needs more work. It has been interesting to work on the mechanical changes we have made in the suspension, and that has given a lot of data to analyse. We still have room for improvement and will work hard to make sure that improvement happens."