The weather had drivers and crews closely monitoring temperature gauges and tires on their high-performance cars.
"It's going to be tough this weekend, definitely," said Lewis Hamilton of Mercedes. "The [hot] weather conditions will not help. Plus, we haven't driven the tires as everyone else has. We've got a bit of catching up to do."
Formula One has not raced since July 7 in Germany, and Mercedes did not take part in last week's tire-test meeting in Great Britain, where a new batch of Pirelli tires was put through the paces. The new tires were created by Pirelli, the exclusive provider to F1, after a spate of blowouts and other failures at the British Grand Prix last month.
The BBC said the Red Bull team appeared to have the best handle on the new tires during Friday's laps on the twisty Hungaroring course in preparation for Sunday's competition in Budapest.
Pirelli this week announced which tires it would provide for the first three races of the second half of the F1 season, which begins Aug. 25 at Spa, Belgium. The circuit takes a three-week break until then after the Hungarian Grand Prix.
Pirelli said the long-and-fast Spa race would be run on the two hardest types of tires used in F1 racing. The next race at Monza, Italy will be run on hard and medium compounds. It is then on to Singapore where the teams will use a medium and super-soft rubber.
"The second half of the season starts off with two of the fastest and most demanding races for tires of the year, in Belgium and Italy," Pirelli Motor Sports Director Paul Hembrey said in a written statement. "Singapore is a completely different challenge: the final street race of the season, which is ideal territory for the super-soft tires."