This has been the coldest January since 1958, when accurate figures were recorded at North Geelong. Even in earlier records I have not been able to find a lower figure than the 16.7 degrees measured then.
From 1957 temperatures were recorded at North Geelong, right next to Corio Bay. You would expect those figures to be moderated slightly by the sea, and they were. But from 1983 temperature figures have been recorded at Mt Duneed – usually warmer in summer and cooler in winter than North Geelong.
But the main characteristic of this summer so far has been its relative coolness. December was only 0.5 of a degree above the long-term normal established at Geelong – 18.5 compared with 18.0 – but January was a full 2.5 degrees below – 16.9 degrees compared with 19.4.
Our January daily average maximum this year was 22.5 degrees – the long-term mean is 25.2. So our days this January were about 2.7 degrees cooler than average. Also the overnight minimum temperatures averaged 11.3 and this was 2.3 degrees below the long-term average of 13.6. When you combine the 2.7 and the 2.3 the average deficit for the month was 2.5.
Geelong’s previous coolest January was in 1958, when the figures were 22.0 and 11.5. In that year the days were slightly cooler than this month – by 0.5 degree – but the nights a bit warmer – by 0.2 degree. Thus this January’s mean monthly temperature ended up being about 0.15 warmer than the lowest.
A slowly moving returning cloud band wrapping around a low pressure system in the Tasman Sea just west of Tasmania brought a stream of heavy rain in the early hours of the 30th, and resulted in up to 80mm of rain in just several hours at Highton. Most other suburbs were similarly affected, but the influence was mainly north-south between Anglesea and Barwon Heads. More northerly stations such as Lara, received around 20-30mm from the system as it headed inland, accompanied by thunder and lightning with some flash flooding.
The Geelong AWS at Mt Duneed received 54mm in the downpour, some of the moisture of which had been fed from the tropical north in Queensland.