Joe Garagiola Jr., Major League Baseball's senior vice president of baseball operations, said that though precipitation was expected, it should not prohibit the contest from beginning at the scheduled 8:37 p.m. ET start time.
"We expect very light showers and intermittent sprinkles," Garagiola said. "Obviously, we want to get in the game, and it looks like we'll be able to start on time tonight."
An MLB official confirmed that, as of 8 p.m., the game was scheduled to start on time. Gates at Citizens Bank Park opened at 5:30 p.m. as scheduled, and both clubs went through an uninterrupted batting-practice session, though drizzle did begin before the field was cleared. Garagiola said that once the game begins, a delay is not anticipated.
"We should be able to play without a stop, as of right now," Garagiola said.
The National Weather Service is calling for rain tonight in the Philadelphia area, mainly after 8 p.m., with a low around 40 degrees and a chance of precipitation at 90 percent. The north wind is between 10-15 mph, and new rainfall amounts between a 10th and a quarter of an inch are possible.
Weather.com, the Web site of The Weather Channel, called for a 100 percent chance of rain from 8-10 p.m., when it reduces to 80 percent and drops to 70 percent at 11 p.m. Temperatures are expected to be in the low-40s to high-30s.
Weatherbug, which provides weather updates to MLB, forecast a 31 percent chance of precipitation at 8 p.m., increasing to 90 percent at 9 p.m. and holding steady there overnight. Temperatures are expected to be in the high-50s to mid-40s.
Though the two clubs have an off-day scheduled for Tuesday, a postponement of Game 5 would not lead to better forecasts in Philadelphia, which is one reason why MLB Commissioner Bud Selig had said that it was important to play Game 3 on Saturday. More rain and showers are predicted for the area.
Ultimately, the decision on when and whether to play remains in the hands of Selig. During the regular season, pregame postponements are controlled by the home club, and then after a game begins, by the umpires. Selig makes those decisions during the World Series.
Game 3 of the World Series, played Saturday evening, was delayed one hour and 31 minutes by rain. The Phillies and Rays played uninterrupted after the delay, with Philadelphia winning, 5-4, in the bottom of the ninth on Carlos Ruiz's bases-loaded infield hit.
The field at Citizens Bank Park is playable in a steady rain. The system in place allows the grass to drain and a sand-like substance is used to keep the dirt portion of the infield from saturating. As a backup, the system is equipped with a vacuum that pumps tons of water out of the drainage pipes.
Games 6 and 7, if necessary, would take place as originally scheduled on Wednesday and Thursday nights, in the domed confines of Tropicana Field in St. Petersburg.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.