On 26 August, TCWC Perth reported that a tropical low had developed on a shear line about 1300 km to the northwest of Cocos Island. Over the next couple of days the depression gradually developed further before at 1800 UTC on 27 August, TCWC Perth estimated that it had become a tropical cyclone and named it Tony. During the next couple of days, the system moved towards the west-southwest before on 29 August it reached its peak intensity of 95 km/h and a peak pressure of 990 hPa as it approached the edge of TCWC Perth's area of responsibility. During the next day, Tony moved into the SouthWest Indian Ocean and weakened gradually before it dissipated during 31 August. Neither the Mauritius or Reunion meteorological services monitored Tony as a tropical cyclone while it was active, while it was not included in the JTWC's analysis of the season.
Viola-Claudette existed from 10 December to 28 December. After passing southeast of St. Brandon, Cyclone Claudette struck Mauritius on December 22, producing wind gusts of. The storm caused 5 fatalities, 257 injuries, and US$175 million in damage on the island. About 5,000 houses were destroyed or severely damaged. Effects on neighboring Réunion were limited to wind gusts and some rainfall.
Hyacinthe formed on January 15, 1980, to the northeast of Mauritius in the southern Indian Ocean. Initially it moved to the west-southwest, and while slowly intensifying it passed north of the French overseas department of Réunion. On January 19, Météo-France estimated that the storm had intensified to a tropical cyclone. Hyacinthe looped to the south of eastern Madagascar and weakened, although it restrengthened after turning to the east. The storm executed another loop to the southwest of Réunion, passing near the island for a second and later third time. Hyacinthe became extratropical on January 29 after turning southward, dissipating two days later. Tropical Cyclone Hyacinthe set several worldwide tropical cyclone rainfall records in Réunion in the Southwestern Indian Ocean, including a peak total of 5678 mm. For twelve days, Hyacinthe dropped torrential rainfall on Réunion; nearly all of the island received more than 1 m of precipitation. Over a 15‑day period from January 14 to January 28, of rainfall were recorded at Commerson's Crater, a volcano. The heaviest rainfall occurred through a process called orographic lift in the mountainous interior, leading to hundreds of landslides. Widespread floods washed out roads and isolated three villages. Hyacinthe caused heavy damage to crops and damaged or destroyed 2,000 houses. Losses from the storm totaled $167 million, and 25 people were killed.
Cyclone Jacinthe
Jacinthe existed from 1 February to 7 February. On February 3, the cyclone passed between Mauritius and Rodrigues, producing wind gusts of and on the respective islands.
Cyclone Kolia
Kolia existed from 25 February to 13 March. The storm executed two loops near the Mascarene Islands, bringing the storm between Réunion and Mauritius twice. Wind gusts reached on Mauritius.
Cyclone Laure
Laure existed from 8 March to 17 March. On March 13, the cyclone passed just east of Mauritius, producing wind gusts of and of rainfall.
