Freddy is expected to make landfall in the northern Mozambique province of Zambezia late Friday or possibly Saturday morning.
"There will be very destructive winds, a very dangerous storm surge on landfall and extreme rainfall over large areas, not just in Mozambique but northeast Zimbabwe, southeast Zambia and Malawi," said Clare Nullis, spokeswoman for the UN's World Meteorological Organization, .
The expected rainfall totals are around 200 to 300 millimeters, but locally it could be more than 400-500 mm over the landing area.
"This is more than twice the usual monthly rainfall and its coming on top of the existing rainfall that Freddy caused the first time around," Nullis said.
"We will obviously need to address if that is a concern in our evaluation," said Randall Cerveny, the WMO's Weather and Climate Extremes rapporteur.
Freddy developed off the north Australian coast and became a named storm on February 6.
The current record is held by Hurricane/Typhoon John, which lasted 31 days in 1994, the WMO said.
Freddy has been a named tropical cyclone for 33 days.
The system has periodically weakened below tropical storm status, such as when it was lingering over Mozambique and Zimbabwe the first time around.
Freddy crossed the entire southern Indian Ocean and made landfall in Madagascar on February 21, crossing the island before reaching Mozambique on February 24.
It tracked over Mozambique and Zimbabwe, bringing heavy rains and flooding.
It then looped back towards the coast, picking up moisture and strength from the warm waters, hit Madagascar again and is now heading back towards Mozambique.
Once it has dissipated, a WMO climate extremes expert committee will assess all the data to determine whether a new record has been indeed set - a process which could take months.
The last cyclones to cross the entire southern Indian Ocean were Tropical Cyclones Leon-Eline and Hudah in 2000.