Jenna Johnson's dancing through another year around the sun ... turning 31 years old Saturday -- and, we've got her hottest shots to celebrate the day.

The "Dancing with the Stars" pro -- who actually met her husband Valentin Chmerkovskiy on the show years ago -- is ready for any weather ... stunning in both a bikini and a flowing dress when the sun's shining.

Sundress season is basically year-round in Los Angeles, and Jenna's always ready to feel the breeze whip through ensembles like this white outfit dotted with strawberries.

Even the colder months can't stop JJ from flaunting her best revealing outfits ... flashing a fierce stare into the camera with glittering Christmas trees stationed behind her.

It's clearly not too frigid in the snap ... 'cause Jenna's still able to wear a crop top and coat combo that is sure to launch happy fans into a jaunty two-step.

Of course, Jenna knows when it's time to get down to business too ... which means switching out sundresses for sweats -- and throwing on workout clothes to practice some of her powerful dance moves.

Jenna's appeared on eight seasons of "Dancing with the Stars" -- and, she's recently become a powerhouse mainstay on the show ... winning twice, including just last season with former 'Bachelor' Joey Graziadei.