Sadie McKenna's bikini pics will keep her fans warm through the coming winter months ... and we've put together a gallery of her scorching sexy shots in honor of her 23rd birthday.

The influencer with more than 1 million followers on Instagram is celebrating another trip around the sun Friday ... and she's spent the past year soaking up the rays -- wearing multiple colorful swimsuits with little left to the imagination.

Check out this photo of Sadie lying back with a pair of bottoms that don't cover her backside whatsoever. She's got a cheeky (pun kinda intended) grin on her face, too.

McKenna also doesn't need to strip down to show off her natural beauty ... looking just as hot in this tight tank top and fatigues combo.

Winter might be coming ... but, at least for now, Sadie's got us feeling pretty darn warm!