Pakistan captain Babar Azam won the toss and elected to field in the second one-day international against England at Lord's on Saturday.
Rain delayed the scheduled 11:00 am (1000 GMT start) by 90 minutes, with the match reduced to 47 overs per side from the standard 50.
England stand-in captain Ben Stokes was winning his 100th ODI cap in the first match at this level at Lord's since he starred in a dramatic 2019 World Cup final win against New Zealand decided by a Super Over.
Both teams were unchanged following England's nine-wicket win in the first of a three-match series at Cardiff on Thursday.
"The different and overcast conditions mean we want to bowl first, and we want to utilise them," Azam told BBC Radio's Test Match Special at the toss.
"We've spoken about Cardiff, and we want the players to play with freedom, be fearless and go and express yourself."
Stokes said he had urged his inexperienced side to carry on from where they had left off in Cardiff.
"I've told them to do the same things as the first match. We didn't really get tested last time out and that usually doesn't happen in cricket."
"We would've bowled first too, there are lovely conditions to bowl here and we've been successful doing it, but this is a good opportunity to see the boys put a score on the board."
As for winning his 100th ODI cap, the all-rounder added: "It comes the more you play but today is a bigger opportunity than for me as an individual. But it's nice to get 100 caps."
England, the reigning 50-over world champions, had to select a completely new squad days before the start of this series after a Covid-19 outbreak among their original party.
Yet a totally changed XI, captained by the fit-again Stokes and featuring five debutants, thrashed Pakistan at Cardiff's Sophia Gardens.
Saturday's match at the home of cricket was the first in England to operate at full capacity since the pandemic.
England: Phil Salt, Dawid Malan, Zak Crawley, James Vince, Ben Stokes (capt), John Simpson (wkt), Lewis Gregory, Craig Overton, Brydon Carse, Saqib Mahmood, Matt Parkinson
Pakistan: Fakhar Zaman, Imam-ul-Haq, Babar Azam (capt), Mohammad Rizwan (wkt), Saud Shakeel, Sohaib Maqsood, Shadab Khan, Faheem Ashraf, Hasan Ali, Shaheen Shah Afridi, Haris Rauf
Umpires: Alex Wharf (ENG), Richard Illingworth (ENG)
TV umpire: Michael Gough (ENG)
Match referee: Chris Broad (ENG)