The 48th AJC Peachtree Road Race will start under a red flag because of the hot and humid conditions, race officials announced on Monday. The alert level is determined by race officials with medical experts.

The red flag, part of the Atlanta Track Club's Event Alert System, is the last level before a black flag.

A black flag is waived if the weather conditions are "extremely dangerous" for runners and causes the race to be canceled. So how likely is a black flag with the pre-race flag already at red?

"By starting at red, we have the ability to message as we are today," Peachtree Road Race Director Rich Kenah said on Monday.

That message to runners is hydrate as much as possible now, and start easy on Tuesday. It's also to ensure racers familiarize themselves on where the fluid stations are throughout the course. Last year, the medical tents were filled to the most in the race's history, according to Kenah. The race started under yellow and was changed to red during the race.

Kenah said a black flag on Tuesday is "very, very unlikely," but it's certainly not impossible. Temperatures are expected to start in the 70s on Tuesday and raise to the lower 80s by noon.

"So we’ve looked very closely at the forecast everyday for the last seven days. There's nothing in that forecast that would indicate that we would ever need to go to a black flag. We don’t anticipate," Kenah said. "It’s always there if we need it."

The flags are located at the starting line as well as at stations throughout the course. In the event of an alert change, the flags will change to the corresponding color, and race officials will give out instructions if the race does go under a black flag.

There will be hundreds of doctors and nurses stationed along the course on Tuesday to tend to the 60,000 participants. Atlanta Police Department, Grady Health professionals, Atlanta-Fire Rescue and EMS all help at the event.

For the first time, race officials are also attempting to chill the 100,000 bottles of water and Powerade at the finish line.

"We have enough water to float a battleship from the starting line to the finish line," Kenah said.

PHOTOS | Crates of water delivered along the AJC Peachtree Road Race