The World Cup match between France and Iraq appeared to be set to start on time after bad weather delayed the opening of the stadium gates.
Heavy rain set in some three hours before the 5pm (2100 GMT) kick-off and thunder claps were also heard.
"Due to inclement weather in the region, gates opening will be delayed," Lincoln Financial Field said on X, advising fans "do not travel to Philadelphia Stadium at this time."
But just over half an hour later an update said that "gates are now open."
Rain and thunderstorms could return at around kick-off time which would set off safety procedures so far not not needed at the tournament but encountered during last year's Club World Cup and World Cup tune-up games.
Based on weather service recommendations on outdoor activities, matches are delayed or stopped for 30 minutes if lightning strikes within 13 kilometres of a stadium. Every further lightning strike sets off the 30 minute rule again.
Players are to leave the pitch and spectators are led to safer areas. Matches are continued in the minute they are stopped when play is possible again.
