Heavy rain in the Northeast on Monday is expected through the evening, and the most severe storms could continue to disrupt the two World Cup games.

As the afternoon progressed into the evening, meteorologists said they were watching for multiple waves of thunderstorms that could bring severe winds and flooding rain. France and Iraq began to play at 5 p.m. in Philadelphia; heavy rain soon sent fans scrambling for cover and delayed the start of the second half for about two hours.

Norway and Senegal started on time, at 8 p.m. in East Rutherford, N.J.

“We’re expecting more development of the showers and thunderstorms, so we’re expecting increasing coverage,” Nick Guzzo, a meteorologist at the National Weather Service in Mount Holly, N.J., said early Monday afternoon.

A severe thunderstorm watch was in place on Monday for an area that stretched from Virginia into New Jersey. The watch could be extended farther north; forecasters said they were coordinating with the Storm Prediction Center, which issues the watches.

Brief tornado warnings were issued for parts of southeastern Pennsylvania, just west of Philadelphia, between 4:30 and 5 p.m. Eastern. By 6, a flash flood warning was in place for an area a few miles north of the stadium in Philadelphia.

The Weather Service forecasters were coordinating with local emergency managers during the 5 p.m. game in Philadelphia. Additionally, two Weather Service forecasters were expected to be present at an emergency operations center for the 8 p.m. match in East Rutherford, N.J., to track potential risks.

“For basically the I-95 corridor north and west, we have the potential of precipitation upward of, like, 70 to 80 percent,” Mr. Guzzo said. (The I-95 corridor is a section of the interstate that connects the major cities in the Northeast, including Philadelphia and New York City.)

These storms will have the potential to produce up to two inches of rainfall per hour — enough to raise the possibility of flash flooding, especially in cities.

While a thunderstorm is possible in New York on Monday evening and at game time, the likelihood of severe weather is slightly lower there than for the Philadelphia game.

Much depends on how far north the warm, moist air can push, said James Connelly, a meteorologist at the Weather Service in New York. If it advances ahead of the later game, there is a possibility for some rumbles of thunder.