The mercury dropped to a low of 9.7 degrees Celsius yesterday morning - the coldest November 18 recorded in urban areas since records began in 1883.
And in Tsuen Wan, the cold spell - caused by an intense northeast monsoon - sent the temperature down to 6.6 degrees.
The Observatory said the chilly weather would continue until the weekend, with today's temperatures expected to range from 11 to 17 degrees. The second coldest November 18 on record was in 1976, when the temperature was 11.9 degrees.
Observatory senior scientific officer Leung Yin-kong said the mornings of tomorrow and Saturday would be cold, at about 12 degrees.
'It will only turn warmer next week, when the temperature will rise to the 20s,' he said.
Despite the cold weather, a few hundred people yesterday camped overnight at the Plover Cove Reservoir in Tai Mei Tuk, to witness the annual Leonid meteor shower, expected to be the best in eight years.
But they were disappointed, as a thick layer of cloud blocked the view. A member of the Hong Kong Astronomical Society said it was unusual to have such thick cloud in November. 'It is so cloudy that there is nothing to see - not even one star, let alone meteors,' one stargazer said.