That is when the interloper from the southwest is set to make its appearance, bringing with it showers and temperatures falling to around 14-15C.
Showers, with some heavier falls, are forecast to dominate Thursday, through the weekend and as far as the following Tuesday.
"It is pretty typical mid-autumn weather," Mr Duncan said, adding that the Bay was not alone as the two last weeks of autumn were looking decidedly damp for most parts of the country.
It was clear local people were making the most of the late splashes of sunshine and T-shirt weather yesterday, with picnic groups enjoying the Hardinge Rd foreshore, and cyclists and walkers taking to the cycleways.
Several youngsters were also spotted swimming at the sandy beach near Napier Port.
The twin cities were well on top of the global weather-boasting charts yesterday.
Many of their Northern Hemisphere cousins, which are only three weeks from the first day of their summer, were struggling to reach respectable temperatures yesterday.
It was 17C and showery in London and Amsterdam, and cloudy and just 11C in Edinburgh.
The more summery cities of Los Angeles and Buenos Aires were also two degrees down on Napier and Hastings. The weather service advice was simple - enjoy it while you can.