That’s one way to stay cool in the summer.

Heidi Klum wore nothing more than a skimpy pair of panties in a July 31 Instagram post, with designer Zac Posen covering up her naughty bits.

“@zac posen . . . I need something to wear for tonight’s @projectrunway @lifetimetv,” the “Project Runway” host captioned the pic. Posen serves as a judge on the fashion design reality TV show, currently in its 13th season on Lifetime.

The former model has a penchant for going topless. In April, the 41-year-old was photographed sans bikini top as she frolicked on the beach in Mexico with her latest beau, 28-year-old art dealer Vito Schnabel.