The state of the four main Niño regions, along with the very strong negative phase reached by the Indian Ocean Dipole, points to highly favourable conditions for summer rainfall until about January.

By Alani Janeke, senior journalist at African Farming and Landbouweekblad

Three of the four main Niño regions – used to determine whether La Niña, El Niño or neutral conditions are developing – are now 0,5°C or more below average. “If this trend continues, as forecasts currently suggest, it could be a very good sign for rainfall in the summer rainfall region during the rest of November, December and the first part of January,” says independent agricultural meteorologist Johan van den Berg.

At the same time, the Indian Ocean Dipole (IOD) has reached very strong levels of a negative phase, which is highly favourable for rainfall over southern Africa. “The index values are among the strongest ever recorded in a negative phase. A fairly strong negative phase previously occurred from August to November 2022.”

Also read: Frequent summer showers forecast from 14 to 25 November

Risk of Flooding

The good rainfall expected until January 2026 increases the risk of large-scale flooding. “The four largest dams in the summer rainfall region are between 93% and 101% full,” Van den Berg says. “On average, these dams’ levels are 23% higher than during the same period last year. For example, the Vaal Dam is currently 101% full, compared with only 33% this time last year. The buffer capacity of these and other large dams is therefore very limited if heavy rainfall occurs.”

Long-term rainfall forecasts indicate very good chances of further rain in November and December over the catchment areas of the Vaal and Orange river systems. “Groundwater levels also remain highly saturated after the heavy rains, especially those that occurred in March and April this year.”

Also read: Good news for farmers: Above-average summer rainfall expected

Fire Risk in Summer and Winter Rainfall Regions

After the summer rainfall season started early this year, the likelihood of veld fires in the summer rainfall region has decreased. The winter months are usually the high-risk season for fires in this region, but only a smaller area burnt this year –despite the large amount of combustible material left after last summer’s heavy rains.

Van den Berg says the main reason for fewer fires was intermittent winter rainfall and above-average rainfall in September.

The winter rainfall region is now in the middle of its fire season. This is largely because below-average rainfall was recorded over the past winter, and conditions have been drying out since August. High temperatures and strong winds since October have further contributed to the fire risk.

“It looks, however, as if rain may fall from around 20 November,” Van den Berg says. “Although it won’t be large amounts, it should increase humidity levels and keep plants and soil moist. Temperatures will also be more moderate, and the likelihood of prolonged heat or heatwave conditions will be much smaller from 23 November and for most of December. This may reduce the fire risk, but with the large amount of dry fynbos vegetation, the danger will remain high.”