The 81-year-old president made the odd and seemingly ad-libbed musing during an economy-focused speech.

“Trump says he doesn’t believe climate change is real. Maybe he should step out here in Vegas where it’s 120 degrees in his bare feet,” Biden said before chuckling at his own remark.

“I don’t want to get going here,” he added.

The gaffe-prone incumbent spoke when it was nearly 110 degrees in Las Vegas. He appeared to stick closely to a speech loaded into teleprompters on either side of his lectern — but looked straight ahead as he dared the Republican presidential nominee to lose his shoes in Sin City, indicating the line may not have been prepared by his speechwriters.

Trump, 78, had his shoes knocked off Saturday during an assassination attempt at a Pennsylvania rally when Secret Service agents rushed to shield him after his ear was grazed by a bullet.

The former president could be heard saying to agents “wait, I want to get my shoes” — just before rising to give an iconic fist pump as blood streamed down his face.

Trump told The Post’s Michael Goodwin in an interview Sunday that “the agents hit me so hard that my shoes fell off, and my shoes are tight.”

It’s unclear if Biden’s colorful commentary about Trump’s footwear was inspired by those comments.

Trump has been equivocal on climate change, saying in 2020, “I don’t think science knows, actually” if the use of fossil fuels is causing global temperatures to increase.

Biden is on a two-day tour of Las Vegas as he tries to reverse Trump’s lead in swing-state Nevada, which the Democrat carried in 2020.

The sitting president spoke earlier Tuesday at the NAACP’s annual conference — where he declared “Donald Trump’s presidency was hell for black America” — and will speak Wednesday to the Latino advocacy group UnidosUS.

Some polls suggest that Trump is gaining ground among black and Latino voters.

Biden is resisting calls from fellow Democrats — including 20 House members and one senator — to drop his bid for a second term in response to concerns about his cognitive fitness following his confused debate performance on June 27.

Some polls suggest that Trump is gaining ground among black and Latino voters.

“What I’m doing is going out and demonstrating to the American people that I’m in command of all my faculties,” Biden told NBC’s Lester Holt in a Monday interview.