Engineers say the landslide count for the past two days is fast approaching the total number for the whole of last year.
Between Tuesday morning and 5.15 pm yesterday, a rain measuring station at the Chinese University near Sha Tin gathered one metre of rain.
The average annual rainfall in Hong Kong is 2.25 metres.
Between Tuesday and 5.30 pm last night there had been 141 landslides compared with 163 for the whole of last year, although officials say that figure was lower than average.
No loss of life had been reported, but eight people were injured in the past 72 hours and rescuers were last night still digging for 73-year-old Ma Shuk-fong who is thought to have been buried in a landslide at the Ten Thousand Buddhas Monastery in Sha Tin.
Dr Andrew Malone, the SAR's Principal Geotechnical Engineer, described the rainfall figures as "unbelievable and remarkable".
He gave details of an emergency contingency plan to cope with a large-scale natural disaster in the SAR. He said an inter-departmental mission would be sent to the next big natural disaster in the region to see evacuation and rescue operations at first hand.
Dr Malone said: "We have been looking at the way Canada dealt with recent floods in Saskatchewan and Japan's earthquake response.
"We feel it is our civic duty to be prepared for an emergency".
He said the Geotechnical Office of the Civil Engineering Department had already sounded out Australian consultants who may form part of the team to set up the emergency response plan.
Meanwhile, major roads were still closed last night as a result of landslides. They included the westbound slow-lane of Tuen Mun Road, Castle Peak Road in both directions near the Lido Beach landslide and both carriageways of Sui Wo Road in Sha Tin.
The Hong Kong Observatory said the rain was expected to continue into early next week.