December 1964:  A warm month. In the North Island the warm temperatures with adequate rainfall produced unusually good pasture growth, though persistent unsettled weather there in mid-month held up haymaking and shearing. In Canterbury and neighbouring areas of Otago and Marlborough rainfall was inadequate and conditions were much too dry. During the last week from Christmas Day to the end of the month, most of the country was favoured with good holiday weather – settled, sunny and warm. A small local tornado caused some damage at Matangi, near Cambridge, on the 18th.

Rainfall: Rainfall was mainly above average in the North Island and below average in the South Island. The greatest surplus was recorded in the central high country of the North Island, with more than double the average. The greatest deficiency was recorded in North Canterbury and Banks Peninsula, with less than half the average value. The month was notable for excessive thunderstorm activity, with some heavy short-period downpours. An exceptional one occurred at Rolleston, near Christchurch, in the early morning of the 21st, when 5 inches of rain was reported to have fallen in less than 3 hours.

 [From the weather sequence: During the period 11th to 17th an anticyclone was centred far to the east, and a series of depressions covered the Tasman sea. Warm moist northerly air brought unsettled conditions with rain especially in western and northern districts. Thunderstorms were reported, with several intense downpours flooding city streets, as in Wanganui on the 15th, Invercargill on the 16th and Napier on the 17th.]

Temperatures: Temperatures were above average – by 2F-3F in the South Island and by 1F-2F in the North Island. The warmest spells were from the 11th to the 17th and in the last week.

Sunshine: Sunshine was 20-50 hours below average in Central Otago and the Southern Lakes district; and 10-30 hours below average in Nelson, Manawatu and Wanganui. Northland, Auckland and Waikato together with the Canterbury plains and coast and coastal Otago were favoured with 20-50 hours above average.

[Some totals: Te Hapua 265, Kaitaia 226, Kerikeri 219, Whangarei 196, Auckland 256, Tauranga 253, Whakatane 239, Taupo 222, Opotiki 222, Hamilton 245, New Plymouth 211, Masterton 234, Gisborne 242, Napier 247, Wairoa 246, Paraparaumu 206, Ohakea 205, Palmerston Nth 190, Levin 182, Wellington 221, Stratford 193, Ohakune 203, Wanganui 204, Westport 210, Hokitika 196, Greymouth 149, Haast 146, Nelson 233, Blenheim 237, Grassmere 221, Kaikoura 232, Mt Cook 175, Mt John 242, Methven 253, Christchurch 218, Tekapo 239, Timaru 198, Waimate 179, Dunedin Aero 179, Dunedin 188, Queenstown 201, Alexandra 196, Invercargill 174, Campbell Is 91, Chatham Is 191].

Sources: NZ Met. Misc. pub. 107 (Climatological table, NZ Gazette) and NZ Met. Misc. pub. 109 (Meteorological Observations) - additional comments by the poster.