The 43-year-old professional from Kings Links in Aberdeen led a charge of sub-par scorers - 21 in all - on day one of the 72-hole Tartan Tour major at Meldrum House Golf Club, Oldmeldrum.
Henderson posted an eight-under-par 62 to dislodge David Law, another former winner, from the lead he had held on a 63.
Henderson, who was out in the worst conditions, knows what it takes to win the Northern Open in inclement weather. In 1996, he won the title in gale-force winds and reinforced the idea that he is not fazed by the elements when he birdied the long fifth and sunk a four footer - his first single putt of the round - at the eighth. He reached the turn in 33 of which 17 had been putts and he came storming home in 29, to alleviate recent concerns about his short game.
"My putting's been letting me down this season and I've lost confidence on the greens, leaving putts well short by being too timid, he said. "But today I seemed to see the lines better and some of the long putts went in.Yes, 62 is my lowest score here. I've been playing okay on the Tartan Tour this season, but the putting has not been as good as the rest of the game. Maybe this is the turning point."
The clubhouse leader had been Law (Paul Lawrie Golf Centre), the winner of the event as an amateur over the same course in 2011, who shot a 63. "I like the course, I feel comfortable on it and it shows in my scores," said the 22-year-old. " I had a 62 the year I won the title but that was from preferred lies. I've got a good record in this tournament because the course suits my eye."
Next best was Graham Fox (Clydeway Golf) with a 64, followed closely by Robert Arnott (Bishopbriggs) on 65. The leading amateur Jamie Savage (Cawder) and David Patrick (Kingsfield) were a shot further back.