The 40-44 Female AG competitor battled tough conditions to finish second out of 30 athletes narrowly behind Swiss competitor Tamara Larizza. King completed the course in six hours, 54 minutes and 53 seconds.
The race included a shortened 1.5 km swim due to cold water temperatures, a 108km bike and a 30km run.
King finished the swim in fifth place with a time of 34:02, and after descending on the steep three-lap bike course that included 1800 metres of climbing, she had risen to third in the standings.
King entered the final running stage with optimism and produced a fantastic time over the 30 km run.
She clocked two hours, 22 minutes and 11 seconds for the final stage and that was enough to give her second on the podium.
King said after the event: “There are no words to describe the emotions that went through my mind as I crossed the finish line. I was in complete disbelief of my performance and what I had just accomplished.
“To finish second in my age group and secure a Silver medal at the World Championships was beyond my wildest dreams.”