The Auckland teenager was advised to pack thermal clothing for the journey south when told how cold it was likely to be.
"I'll be going shopping for something cooler to wear now," she said after her victory.
Despite being an early favourite for the junior women's under-19 title, Trevis (18), a first year sport and exercise science student, was by her own admission heading into the unknown, as she was unaware of the final make-up of the field and, despite knowing most of the girls, was not sure what sort of form they were in.
But right from the start Trevis allayed any pre-race concerns, settling into a solid pace at the head of the field.
By the mid-way stage of the 5km title race, she was looking secure and holding a 20m lead on nearest rival Barbara Roy (Otago), with the pair leaving the remainder of the field jostling for bronze.
Despite a strong fightback from Roy, Trevis proved too strong over the closing stages, finishing in 17min 8.60sec, with Roy second in 17min 39.30sec and Lydia O'Donnell (Auckland) winning the battle for third in 18min 9sec.
Shortly after Trevis won the junior women's title, Otago had plenty to celebrate when Anna-Lisa Uttley crossed to win the national under-16 title on the same course in 17min 30.60sec.
It was a command performance from Uttley, who last month won the national under-16 cross-country title in Christchurch.
Finishing second to Uttley was Sally Wilkins (Auckland), with Ashleigh Williams (Auckland) third.
The men's under-16 title, contested on the 6km course, gave witness to another command performance, this time from Mohamed Ali (Waikato Bay of Plenty), who despite a challenge from his regional team-mate, Michael Sutton, over the middle stages, recorded a convincing victory in 19min 31.47sec.
Sutton was second in 19min 43.27sec, with Sean McCrudden (Wellington) third in 19min 54.54sec.
Ali emulated Uttley in winning the national cross-country and road double in little over a month.
A tactical battle in the junior men's under-19 on the 8km course helped dethrone defending champion Eric Speakman (Hawkes Bay Gisborne).
In a race with plenty of surges and lead changes, it came down to a battle over the final 1500m.
Auckland's Jono Jackson's tactic was to put in a sprint 200m out and hope to hold on, knowing Speakman is a fast finisher.
It was this tactic that paid off for the Barry Magee-coached Jackson, who got the jump he needed to finish in 25min 31.43sec, with Speakman hot on his heels just 0.45sec back.
Third was the highly promising Harry Dixon (Tasman) in 25min 35.25sec.
