At 5:08 p.m. yesterday, as officials searched the heavens for a sign that the show might go on, four men huddled in back room of the National Park Service command post on the Washington Monument grounds.

Outside, a light, misty rain fell steadily beneath said, gray skies. Hundreds of wet, bedraggled-looking tourists, Yippies and Washington residents milled about, waiting for The Decision: Go or No Go.

Inside the bunker, the phones rang constantly as anxious Washingtonians jammed the park service switchboard, trying to find out whether the traditional Fourth of July fireworks estra-vaganza on the Mall would blast off on schedule.

"we don't know yet," park service technician Terry Barbot, 24, told the umpteenth caller. "Listen to your radio between 6 and 6:30 p.m."

But the decision came sooner. At 5:14 the door opened, and fireworks impresario Felix Grucci Jr., park service spokesman George Berklacy, performing arts coordinator Gene Kassman and National Capital Parks Superintendent Roger Sulcer emerged.

The show, they announced, would be postponed until 9:15 tonight, one of two rain dates called for in the contact -- an evening that, according to the National Weather Service, was expected to be clear, cool and fit for the $20,000 blast.

"an artist wouldn't draw on a dirty canvas, and we don't want to explode our fireworks on an impure sky," said Grucci, 27, whose family has been blowing things up for 125 years.

He remembered all too well, though, the embarrassment 10 years ago when officials called off the fireworks for rain at 5 p.m. -- only to have skies clear up immediately thereafter.

"forecasting the weather is a black art and today we just couldn't seem to get a reading," said Kassman, a distinguished gray-haired presence in a blue blazer and Dior tie. "That's what made us antsy and anxious. But the grounds are soft and wet. It would be uncomfortable."

All day long, tension inside the granite bunker rivaled that of Cape Canaveral before a launch, as the cold air mass from Canada that had commingled with the warm air of the Ohio Valley moved east and Washington skies turned gray and drizzly.

"let's cancel the thing and get done with it," Kassman snapped at one point.

Grucci said he had three hours' worth of electrical wiring works left for the "big blast" finale of reds, whites and blues, chrysanthemums, peonies, and croisettes when the rain had forced him to put the countdown of hold.

The explosivrs were covered with waterproof plastic and nailed down. If the weather had looked as if it might clear, Grucci figured he would have just enough time to wire up the display if he started at 6 p. m.

But the weather had driven away the crowds and every maestro yearns to have an audiennce.

"even if it had gone off as planned the crowd would not have been there to see the pagneantry," Grucci said. "It would be disappointing to shoot off fireworks in wheather like this.

"you'd lose all the color of the brilliant magnesium whites and soft pastel blues if you shot into this mist. It just wouldn't be the same show."

So tonight on the Mall, Grucci will try again. And if it rains tonight, he will try tomorrow night, as the contract specifies. And will be the last chance he gets.