The overall winner of this year's Outdoor Photographer of the Year competition braved a brutal snowstorm to capture an incredible shot of sheep sheltering from the elements. Selected from more than 20,000 entries, the image illustrates the extreme challenges outdoor photographers face.

The competition spans 10 categories, from landscapes and wildlife, to adventure sports and macro, but if there is one overarching theme to be found it seems to be a focus on the extraordinary lengths photographers go to capture impressive moments from nature. Alongside individual category winners receiving £500 (US$660), the overall winner also collects £2,000 (US$2,600).

"The judges were blown away by the quality of work that we looked at this year, and it shows that the world of outdoor photography is thriving like never before, thanks to the hard work, fresh thinking and deep passion brought by the photographers," explains Steve Watkins, head judge and editor of Outdoor Photography magazine.

UK photographer Robert Birkby took the top prize in this year's competition with a frosty shot snapped during a massive snowstorm in West Yorkshire England. Birkby's shot perfectly encapsulates the challenges of extreme outdoor photography, using a fast shutter to capture falling snowflakes and conveying a truly chilly sense of being in the middle of a gusty storm.

"Robert's image captures just about every aspect of what is required to be a top-level outdoor photographer; from the willingness to go the extra mile to be out there shooting in extreme conditions to the calmness and clear thinking then necessary to pull together a technically brilliant and creatively compelling composition," says Watkins. "All of the judges had an immediate and strong emotional response to his image, which manages to combine the chilling feeling of being there in the blizzard with the slightest hint of humor at the hopeless predicament of the hardy sheep."

For a smaller photography competition, the Outdoor Photographer of the Year has collected a truly astonishing group of winners, rivaling any competition on the annual calendar. Other winning highlights include a mind-bending shot of two tiny climbers climbing El Capitan in Yosemite, a surreal snap of a cave diver navigating an alien-like underwater landscape, and a stunning drone-captured image of a bear surrounded by salmon in a Russian lake.

Take a look through our gallery featuring all the winners and commended images from this year's strong competition.

View gallery - 35 images