October Weather. If you plan on visiting New Zealand during October, then you are onto a good thing weather-wise. From October onwards, the capital city Wellington enjoys its best weather – with average temperatures of between 17 and 21°C. However, Wellington is well-known for being the windiest city in New Zealand – the strongest wind recorded was in the month of October (a gust of 215km/h). Do not declare 'summer' too soon!