For about an hour or so this morning, the Cooper River Bridge Run and Walk will have a population equivalent to South Carolina's seventh-largest city, Sumter, as participants take part in an historic and expected record-breaking event.

Barring severe weather that could cause some of the masses to stay home, about 35,000 to 40,000 people will run or walk in the last Bridge Run on the Silas N. Pearman Bridge, which is slated for demolition. Next year's event will be on the new Arthur Ravenel Jr. Bridge.

Weather forecasts for the hours leading up to Saturday's 8 a.m. start call for a 30-40 percent chance of rain, temperatures in the low 60s and 15 mph west winds, according to National Weather Service Meteorologist Bob Bright.

"There will be nothing in terms of severe weather," said Bright, adding that the weather will clear, cool a bit and be more windy later in the morning.

Race Director Julian Smith and Assistant Race Director Howie Schomer speculated that rainy weather would deter some walkers, but that most runners would show up.

"The weather won't change the main reason people want to run this year and that's to do the (Pearman) bridge one last time," said Schomer.Rain never has fallen during the event's previous 27 years, according to Bridge Run historian Cedric Jaggers, but it rained up until the start of one year's race.

As of 2 p.m. Friday, 24,525 people had signed up for the 10K race, 17,250 for the 7K walk, and 788 for Friday's Kids Run events, according to the Bridge Run's computer guru Chris Pertgen.

He said the 10K number was below the 25,000 cap, which officials said was met on Tuesday, because some registrations still needed to be punched in the computer and because officials saved some numbers for a cushion.

While 42,000 have signed up, a small chunk of those people won't show up. In typical road races, 10-20 percent of the people who sign up don't participate or finish the race.

For example, 15,229 of the 17,311 registered runners finished last year. However, in popular races like the Bridge Run, unregistered participants, or "bandits," add an uncountable number of participants to the horde crossing the bridge.

As expected, several out-of-towners showed up at Friday's Bridge Run Expo to register for the race only to find it was capped. Because some run and walk participants turned their numbers back into officials, staffers and volunteers were able to sign some of them up.

Assistant Race Director Tami Varn said one was a Lutheran minister who carried a sign saying something like, "Desperately need two running tickets."

Volunteers signed him up. Three women from Houston flew into Charleston for the event, and they lucked out, too.

Even some South Carolinians were unaware of the new participation caps, including Jim Frazier of Myrtle Beach.

Frazier ran his first Bridge Run in 1994. He has run it many times since then and become accustomed to signing up on the Friday before the race.

"When someone told me there was a cap, I thought it was an April Fool's joke," said Frazier, who ended up getting a number. "I have to run this year's race, even if it rains, because it's the last one on this bridge."

Frazier is among 300 who decided to sign up for the 2006 Bridge Run, which will be the first on the Ravenel Bridge and is expected to be as popular as this year's run.

Though the weather threatened Friday's Kids Run event at Hampton Park, the predicted rain and thunderstorms held off. About 1,000 children, including about 200 who signed up at the park, participated in fun runs ranging from 25 yards to 1-mile.

One semi-regular bridge runner, Gov. Mark Sanford, won't be running this year due to a back injury he suffered after clearing some brush at the family farm last week. However, First Lady Jenny Sanford and their four sons will participate.

Sanford said in a press release, "I'm obviously disappointed about not being able to do the Bridge Run this year. It's a great event that I've run many times over the years, but after overdoing it, I need to spend Saturday being a fan to Jenny, the boys and (40,000) others."