South Pacific Islands: Annual rainy season to occur across the region through at least April 30

The annual rainy season will run through April, bringing an elevated threat of heavy rainfall, strong winds, flooding, and landslides/mudslides to the South Pacific Islands. Meteorological agencies may issue weather warnings, particularly if extreme rain, severe thunderstorms, or strong winds are forecast.

Heavy downpours, flooding, and landslides could affect business, transport, and utility services in many areas. Localized disruptions could persist well after hazardous events have concluded; floodwaters may take days to subside, and debris from mudslides may take weeks to be cleared. The risk of flooding is highest in low-lying communities near waterbodies in recognized floodplains. Rivers could flood during periods of intense rainfall. Fiji and Vanuatu have several rivers, including the Jordan, Lololima, and Sarakata rivers in Vanuatu and the Ba, Dreketi, Nadi, Nanuku, Navua, Rewa, and Sigatoka rivers in Fiji. The Solomon Islands and New Caledonia have several rivers and lakes, including the Lunga, Matanijau, and Tenaru rivers and Lake Tegano in the Solomon Islands and the Diahot and Dumbea rivers and Yate Lake in New Caledonia. Tonga and Cook Islands do not have any rivers, but Niuatoputapu and 'Eua islands in Tonga and the larger islands in the Cook Islands contain creeks. Flash floods, which can occur with little to no warning, often threaten communities downstream of major rivers or dams in the event of structural failure. Urban flooding is possible in areas with poorly maintained or inadequate drainage systems, while storm surges may trigger flooding in coastal areas. Landslides and mudslides are possible in hilly and mountainous regions.

Tropical systems, including tropical depressions and cyclones, may pose additional threats during the rainy season. Tropical systems usually prolong or aggravate disruptions already caused by heavy rainfall.

Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas, especially in rural areas, where infrastructure is already of a poor standard. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Significant downpours could trigger flight delays and cancellations at domestic and international airports. Authorities may temporarily suspend port operations if strong winds cause hazardous sea conditions.

Localized business disruptions may occur; some businesses might not operate at full capacity because of flood damage to facilities, possible evacuations, and some employees' inability to reach work sites.

There is an elevated threat of disease outbreaks during the rainy season. Backflow from drains mixed with floodwaters can become trapped in open areas when inundations recede. These stagnant pools often become breeding grounds for mosquitoes and bacteria, increasing the incidence of insect- and waterborne diseases. Exposure to contaminated water from inundated industrial sites, sewer systems, and septic tanks also poses a significant health threat.