Africa: Annual rainy season likely to cause increased flood threat and localized disruptions across southern regions through April

Southern Africa will experience periods of heavy rainfall during the annual rainy season through at least late April. Affected countries include Angola, Zambia, Zimbabwe, Botswana, Namibia, South Africa, Lesotho, and Eswatini.

A few areas, including the Northern and Western Cape provinces of South Africa, the desert regions of western Namibia, and the Makgadikgadi Pan Desert of Botswana, are unlikely to experience a major impact from the rainy season.

The heavy rainfall period will increase the risk of flooding and landslides. Meteorological agencies throughout southern Africa may issue weather warnings, particularly if extreme rainfall, severe thunderstorms, or strong winds are forecast.

The risk of flooding is highest in low-lying communities near watercourses in recognized floodplains. Southern Africa has several major rivers, including the Limpopo, Molopo, Nossob, Orange, and Vaal, which could flood during intense rainfall. Flash floods can occur with little to no warning and often threaten communities downstream of major rivers or dams in the event of infrastructure failure. Even relatively low amounts of precipitation can trigger flood events in areas where dry, compacted soil cannot absorb runoff. Storm surges may trigger flooding in coastal areas. Landslides and mudslides are possible in hilly and mountainous regions, including the Drakensberg (South Africa, Lesotho, and Eswatini) and Witwatersrand mountain ranges (South Africa and Botswana). Localized disruptions will likely persist well after hazardous events have concluded; floodwaters may take days to subside, and clearance of resulting mudslide debris could take weeks.

Communities with poor or a lack of stormwater drainage systems may experience urban flooding during significant rainfall, while areal flooding may threaten sites near rivers and streams - particularly those within recognized floodplains. Deadly flash flooding is possible following torrential downpours, especially in vulnerable communities near the edge of watercourses.

Floodwaters and debris flows will likely 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 will cause hazardous driving conditions on regional highways. Authorities will probably temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather will likely trigger flight delays and cancellations at domestic and international airports. Authorities will probably temporarily suspend port operations or close beaches if strong winds trigger hazardous sea conditions. Flooding will likely block regional rail lines; freight and passenger train delays and cancellations are likely in areas that experience heavy rainfall and track inundation.

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

During the rainy season, disease outbreaks are more likely to occur. 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.