Exactly this....
you need to pack for everything, hot sun, sunscreen, poring rain, jackets & jumpers.
We were VERY lucky on Ovation depart Sydney on 23 Dec 2022.
flat calm for the first 10 days, 24 degrees & sunny in the sounds & Dunedin, Christchurch & Tauranga.
missed Bay of Islands stop & was too rough to tender.
Another perfect 3 days cruise home, with a 25 knot easterly pushing us back to Sydney
was great!