Chelsea boss Enzo Maresca said on Monday it has been “impossible” to organise normal training sessions amid a “code red” severe heat warning in Philadelphia.
A heat wave across eastern North America has seen people hospitalised with heat-related illnesses and weather warnings covering an area affecting 160m people.
Heat concerns have been raised by other managers at the Club World Cup, while campaign group Fossil Free Football has warned of players being put at risk by competing in such conditions.
Governing body Fifa has said “the health of everyone involved in football” is its “top priority”, with its medical experts in regular contact with the clubs taking part.
Additional cooling breaks have been introduced in games.
Both City and Juventus have already qualified for the last-16 stage of the competition with two victories apiece, but the Serie A side sit top by virtue of one more goal scored.
Their finishing positions in Group G will be important heading into the knockout stages as one of the sides will next come up against La Liga giants Real Madrid.
After the opening game win over Wydad AC, Guardiola played an entirely different starting XI in the second match against Al Ain and says he will ring the changes once more.
City will be without midfielder Claudio Echeverri, who is expected to miss two to three weeks after sustaining an ankle injury in the previous game, while defender Rico Lewis is suspended.
The Spaniard said: “We will play new players and in the next game too and in the second half. The selection has that in mind.
“In these conditions we are not ready to play 90 minutes and at half-time we will make substitutions.”
There has been criticism about large banks of empty seats in stadiums during the group stages of the Fifa tournament.
This match is being held at the exposed 60,000-capacity venue which offers little cover for spectators in the stands.
“Two big clubs and hopefully there will be people,” said Guardiola. “Last 16, quarter-finals, semi-final, final – hopefully the stadiums will be full.
“But 70,000, 80,000 – it is not easy to hold the crowd. Hopefully we can do a good game and the people can come.
“Bring water, hats, towels on the necks – it will be tough.”