First aid tents all over town will assist any visitors and event participants who run into problems from the muggy and warm temperatures.
Visitors can take free shuttles into downtown and re-enactments. The National Park Service also offers shuttles and satellite parking.
Traffic flow on Friday, the first full day of 150th events, went well.
Thousands of re-enactors go back in time
Don Ernsberger led the building of a replica Pickett's Charge stone wall for this weekend's re-enactment at Bushey Farm.
Seventy volunteeers shaped 88 tons of stone to re-create the focal point of the march.
"The Confederates captured that angle for about five to eight minutes and the Union reinforcements came in and pushed them out."
Ernsberger, who authored a book about the wall and the attack, will portray a Union lieutenant on Sunday.
"I wrote this book three years ago and I hope to see it happen before my eyes," he said.
An estimatetd 10,000 re-enactors are on hand at Bushey Farm this weekend, said Kris Shelton, media and marketing coordinator for the Blue Gray Alliance, which is sponsoring the event.
The first mock battle went well Friday, said Shelton, who said organizers have detailed logistics plans for the maneuvering of troops at the site.
There's a chance of rain for the next several days.
"We are historically accurate, but we don't control the weather," Shelton said.
Organizers expect tens of thousands of spectators on Saturday and Sunday.
Besides portrayals of the fighting, the re-enactment will include about 200 individuals representing the town of Gettysburg in 1863.
"The civilians living there have done careful research of the residents of the town and they have taken on their identities, including their trade and craft," said Shelton.
Safety of participants and guests comes first, but authenticity also is a priority.
"People are here to recognize and honor and commemorate what these people went through, the sacrifices of both soldiers and civilians," said Shelton.
The battles draw re-enactors devoted to donning the proper uniforms and equipment. They can get caught up in the heat of the battle and emotional or significant moments.
"That intensity is something that really sparks re-enactors," she said. "That combined with leaving electronics and the modern world behind."
Visitors and participants alike understand that real people died in battle -- that freedom had a cost.
Making the battlefield historically accurate
While battle re-enactments are not permitted on National Park Service sites -- the commemorative clashes will be on privately owned land -- such events and the visitor experience at Gettysburg National Military Park are "not mutually exclusive," said Litterst.
"We want that excitement to spill over to the sites and grounds where the events actually took place," he said.
The National Park Service does not provide crowd estimates or projections, but it's clear the park will be busy over the next week, given ranger-led hikes and special programs.