The championship leader said the searing heat during the afternoon session had been tough to endure, but was happy his car had survived without any serious problems.
“I don’t think I’ve been to Spain when it’s this hot,” he said.
“We’re here in February and March usually, or early May.
“It’s beautiful weather, but it’s a killer in the car and it’s obviously very tough on tyres as well.”
The six-time world champion had been second behind Bottas after the morning’s opening session, but re-established his supremacy on a hot afternoon at the Circuit de Catalunya.
Hamilton clocked a best lap in one minute and 16.883 seconds to outpace Bottas by 0.287 seconds with Max Verstappen, winner of last weekend’s 70th Anniversary Grand Prix at Silverstone, third for Red Bull, eight-tenths adrift of the fastest lap.
In much hotter conditions than those of the morning, with an air temperature of 30 degrees Celsius and the track at almost 50, the two Mercedes enjoyed a comfortable advantage over their rivals.
– ‘Hottest here’ –
“It looks like things will be very exciting with Red Bull over the long distance,” said Hamilton, referring to the race.
“It will therefore be a very exciting race, I think.
“It’s definitely quite tough out there. It’s the hottest that it has been for us here.”
Despite the heat, he said he was generally satisfied.
“It’s been a good day – the second session was better for me. The long runs we look very close with the Red Bulls so I think it’s going to be a very close race.
“The tyres aren’t happy in these conditions so you’re just sliding around with overheated tyres. I didn’t see any blistering, but we didn’t see blistering last Friday either so I really can’t say too much.”
Bottas, keen to regain lost ground after slipping to third behind Verstappen in the title race last Sunday, was also ambiguous about his prospects.
“I didn’t have a bad feeling in the car,” he said.
“I struggled with a bit of under-steer at the beginning of the session, but that’s normally a quick fix with the car set-up, but it was quite a lot by the end.”
Verstappen was similarly unconvinced that anything meaningful had been revealed on Friday.
“The car was ok on one lap,” said the Dutchman.
“We are using all of the hardest compounds and it is manageable. We would have liked to have a softer tyre, but they’re not here this weekend.
“Mercedes are very fast on one lap in qualifying, but let’s see what their race pace is like on Sunday. I think it’s going to be very different to last week at Silverstone.”
Daniel Ricciardo was fourth for Renault ahead of Romain Grosjean of Haas who outpaced Charles Leclerc, who was sixth for Ferrari.
Carlos Sainz was seventh for McLaren ahead of Sergio Perez, returning to action for Racing Point after missing two races with coronavirus.
Esteban Ocon in the second Renault and Pierre Gasly of Alpha Tauri filled out the top ten.