They say Father Time is undefeated in the world of sports, but it’s Mother Nature the UFC may have to contend with Sunday night on the South Lawn of the White House.

A roughly 40 percent chance of scattered thunderstorms looms in the Washington forecast, per Weather Channel as of Saturday evening, for the 8 p.m. start of the outdoor UFC Freedom 250 event.

That’s an ill omen for the fighters and 4,300 spectators composed largely of military servicemen expected to attend, though at least by 11 p.m. the threat of lightning drops off the hourly forecast and shifts merely to a 45 percent chance of showers.

UFC CEO Dana White, who strongly prefers to hold events at indoor arenas, has vowed that only lightning could halt the action in the cage, which is situated under a hulking steel structure painted in stars and stripes dubbed “The Claw” that both provides some protection from rain and supports the production’s lighting, sound system and big screens.

“I don’t care if it snows, rains, whatever; we’re going,” White told reporters Tuesday. “And even lightning. You guys all played sports when you were growing up — whenever there was lightning, you’d sit the lightning out, and then when it was over, you played. That’s what we’ll do.”

Typical D.C. high humidity is expected as well, something which many of the athletes prepared for during their respective training camps by spending more time training outdoors.

Justin Gaethje, the interim lightweight champion aiming to become the unified and undisputed UFC titleholder with a win against Ilia Topuria in the main event, told The Post he mixed in plenty of sauna time around workouts as a means of preparing his body for what could be in the neighborhood of 80 percent humidity and projected temperatures in the 74-80 degree range for the planned duration of the event.

But a slippery canvas is not at all a concern for Gaethje, even as the potential exists for strong gusts to blow potential precipitation into the Octagon.

“I don’t think that there’s a scenario where we’ll fight that the canvas is wet,” Gaethje said before adding a caveat, “other than with other people’s blood.”