🇷🇪Réunion

Réunion is a French overseas department and island in the southwestern Indian Ocean (approximately 2,512 km²) located at 21°S, roughly 700–800 km east of Madagascar. Dominated by two volcanic massifs, Piton des Neiges (3,070 m, the highest peak in the Indian Ocean) and the actively erupting Piton de la Fournaise (over 2,600 m, one of the world's most active volcanoes), the island rises from tropical coastlines to alpine summits within 40 km.

This extreme topography creates dramatic climate zones: tropical humid (Af / Am) along the windward coastal lowlands with hot rainy summers and warm drier winters, a much drier leeward west coast, subtropical highland (Cfb) in mid-elevation cirques and plateaus, and cold alpine conditions near the summit of Piton des Neiges.

Réunion holds world rainfall records with Foc-Foc station recording 1,825 mm in 24 hours (7–8 January 1966) and Commerson Crater recording 6,083 mm in 15 days during Cyclone Hyacinthe (1980), plus multiple other duration records recognized by the World Meteorological Organization.

Saint-Denis (capital, coastal) sees July highs of about 25°C with nights near 18°C and January highs of 30°C with nights near 24°C, with 1,600 mm rainfall concentrated November–April during the cyclone season. Saint-Pierre (southern coast) sees July highs of about 26°C with nights near 16°C and January highs near 32°C, with 650–950 mm, the drier leeward side. Cilaos (inland cirque, 1,200 m) sees July highs of about 19°C with nights near 7°C and January highs of about 26°C with nights near 15°C, with about 1,800 mm.

Le Port and Saint-Benoît see July highs of 25–27°C with nights of 17–19°C and January highs of 30–32°C with nights of 22–25°C, with about 540–3,500 mm depending on windward exposure. Piton des Neiges summit is cold in July, with frost and occasional snow. Réunion lies in the South Indian Ocean cyclone basin: severe events include Cyclone Hyacinthe (January 1980, 25 deaths, 6,083 mm rainfall at Commerson Crater in 15 days, severe floods and landslides), Cyclone Gamède (February 2007, over 5,000 mm at Commerson Crater), Cyclone Belal (January 2024, major flooding and power outages, red alert issued), Cyclone Batsirai (February 2022, power outages), recurrent coral bleaching in the lagoon reefs, sea-level rise threatening Saint-Denis and coastal infrastructure, and increasing tropical cyclone intensity trends under warming ocean conditions.

Our archive covers 2 Réunion cities with daily ERA5 reanalysis data going back to 1940. Comparing the last decade against the 1940–1970 baseline, mean temperatures across these cities have risen by about 0.8°C.