One person was still reported missing two days after heavy rain and high winds flooded homes, but the number of people in emergency shelter had been reduced from 2,700 to 1,700, Italy's civil protection agency said.
"The search for the missing person continues, as does the rescue operation. We think the road network will be usable by the end of the day," a member of the agency's press office said.
The death toll of 16 was revised down from a figure of 18 announced by government on Tuesday.
Rain continued to fall overnight but caused no further damage to buildings or bridges on the island.
Olbia, a popular holiday destination in the summer months which was left almost entirely under water, declared a day of mourning and began organizing funerals for six of the flood victims.
The bad weather crept across onto the mainland, flooding streets and felling trees in the south of the country, from the Calabria region to the capital.
Authorities in Calabria were preparing to declare a state of natural disaster after "floods and landslides which have caused damage and constitute a danger" for inhabitants.
In Rome, firemen were called out 150 times during the night to remove fallen trees from roads and pump water out of cellars. Ferries between Naples and nearby islands were also halted.