Olivia Culpo Bikini Photo Shoot In 115 Degrees!!!

Don't think bikini models are tough? Try striking poses all day long in a 115 degree desert ... like Olivia Culpo!!!

The former Miss Universe set up shop in Palm Springs on Sunday for a photo shoot with Vital Proteins ... where she had to pretend she wasn't bothered by the scorching heat!!

Don't worry, Olivia had umbrella holders and people with water bottles waiting on the set to spray her down any time she overheated.

The good news? She pulled it off ... the photos are straight fire!!!

It's the first time we've seen Olivia back in the U.S. since her vacation with boyfriend Danny Amendola.