So, after one lap, drivers all came back into the pits to switch tyres which caused a delay in the first times being set.
However, eight minutes in, Sainz became the first driver to set a time with a 1min 51.622sec on the hard compound, while his team-mate could only achieve 0.050sec slower on his opening lap.
However, the Ferrari drivers soon started to fall down the order with the soft tyre clearly the quicker compound in the opening stages.
Norris went 1.9 seconds faster than Sainz, Alonso slotted in just behind the McLaren driver by two-tenths but Verstappen then stormed to the top, beating the Briton by 2.256 seconds.
However, Ferrari decided to stick with the hards while Red Bull also fitted the same compound to Perez and as time went on, they got themselves back up the order to go third, fourth and fifth after 25 minutes, with Hamilton was in second on the mediums.
During that time Esteban Ocon was forced to retire from the session following a transmission problem with a 1min 50.315sec being his best lap time at that point.
Then in the second half of the session, all the drivers decided to go with the soft tyre which caused changes at the top.
Sainz went first with a 1min 46.538sec in a Ferrari one-two, Verstappen fell down to third with Russell in fourth eight-tenths off the lead, while Stroll had done well to get himself inside the top five.
The session then came to a halt with 23 minutes left after Kevin Magnussen became the second retiree from FP1.
An engine issue suddenly struck at the exit of the final corner, before he eventually lost all power just out of Turn 1, leaving his car stopped on the sideline.
Despite the red flag, however, the time continued to tick and there was just nine minutes left on the clock when the session resumed.
Now with an increased risk of rain, all the drivers wanted to get out on track with a mixture of the soft tyre, or mediums being used.
However, conditions very rapidly changed before the session ended and it was not the weather for slicks.
This meant there was no change in the order as drivers all tumbled back into the pits before they could even start a hot lap.
The heavens opening towards the end of the session, meaning a bit of a shakeup in the order with Alex Albon in sixth, ahead of Daniel Ricciardo in seventh, Yuki Tsunoda eighth, Lewis Hamilton ninth and Sergio Perez rounding up the top ten.
Sainz, Leclerc and Verstappen lead the way after first practice… 👊#BelgianGP #F1 pic.twitter.com/ZgIKhpIAL4
— Formula 1 (@F1) August 26, 2022
FP2
Despite the downpour at the end of FP1, the second practice session started off dry and drivers rushed out of their garages with all three tyre compounds being seen on track.
Verstappen set the pace after the opening 15 minutes with a 1min 46.850 sec lap, half a second quicker than Sainz, with Leclerc in third, 1.2sec off the Red Bull.
All three drivers started on the medium tyre and Perez was in fourth on the same compound, just one-tenth off Leclerc.
Mercedes meanwhile, who is expected to fight closely with the front-runners, struggled at the start with both drivers on the hards and Russell complaining about tyre temperature.
Hamilton was tenth after 15 minutes, with Russell six below as Tsunoda, Norris, Zhou Guanyu, Ricciardo and Alonso separated Mercedes from the two leading teams at the time.
With rain forecast, drivers were racking up laps while it remained dry, leaving the pitlane quiet.