Ta Kwu Ling in the northern New Territories was covered in frost yesterday morning as temperatures plunged to 1.9 degrees Celsius - the coldest day in the area this year.
Other districts in the New Territories were also hit by the cold snap, with temperatures at about five degrees in Tai Po and seven degrees in Sheung Shui yesterday morning.
"Hong Kong is being affected by the cold wind from the mainland," the Observatory's scientific officer Tsoi Tze-shun said yesterday. "It will get warmer gradually as Hong Kong will be getting the easterly wind, which comes from the ocean and is warmer."
The Observatory's forecasts say the temperature will be between 10 and 16 degrees today and between 12 and 17 degrees tomorrow.
Temperatures will rise gradually and reach between 14 and 18 degrees on Sunday.
Yesterday morning in Ta Kwu Ling, cars and farmlands were covered in frost.
A farmer who grows watercress and lettuce in the area was worried about the impact the frost might have on his vegetables. While the frost would not kill his crops, it would likely delay their harvest, he said.
A thermometer on his farm showed that the temperature had dropped to minus 0.5 degrees yesterday morning.
"There is nothing I can do in the face of a natural force," he told i-Cable News.
Between midnight and 5pm yesterday, 1,194 elderly people activated the personal emergency buttons linking their homes to the Senior Citizen Home Safety Association control centre.
Of the callers, 92 were taken to hospital, mostly because of breathing difficulties.
Separately, the Observatory forecast that temperatures this morning would be between five and 15 degrees in Guangzhou; nine and 16 degrees in Shenzhen; and five to 16 degrees in Huizhou .