Sheldon Strydom, Rhodes University
Clara Hickman, African Mountain Research Foundation
On the 16th of May, 2025, the South African Weather Service issued a media release detailing the forecasted icy conditions expected over the country over the next week. Two cold front systems were approaching the country, with air temperature expected to drop significantly between the 19th and 23rd of May. A drop in freezing levels across the Eastern Cape and KwaZulu-Natal provinces was expected to result in snowfall along higher elevations of the South African escarpment, as well as into Lesotho (see Figure 1). Snowfall is not rare in South Africa, but not every cold front system results in snow. As a result, warnings are often issued when snowfall is likely as it can be disruptive and dangerous.
The month of May in South Africa is when winter conditions really start to set in. In late spring and autumn some weaker cold fronts can move over the country (and cut-off lows too) but temperatures tend to recover somewhat after their passing. In May, temperature tends not to recover as well and winter synoptic systems can result in low minimum air temperatures. May of 2025 has not been any different, with a number of days approach freezing levels, the earliest being between the 3rd and 4th of May. Another notable drop in air temperature occurred on the 12th of May, bit that day too did not manage to reach freezing levels (see Figure 2). Some snow (and thus freezing temperatures) has occurred in Lesotho in 2025, but these have been limited spatially.
Snowfall accumulation model forecasts(ECMWF 9km) on Monday (20th of May) indicated that freezing levels might fall below 2100 m, with snow forecast for much of Lesotho and the sounding mountains along the border with South Africa. Often these snowfall models overestimate the amount of snow, but are usually a good indication of icy conditions (see Figure 3).
As expected the first of the two cold front systems moved closer to the Lesotho and the Drakensberg mountain on the 20th of May (see Figure 4). The satellite image for the day, recorded by NOAA-21/VIIRS, and output as a Corrected True Colour Reflectance image shows the passage of the two frontal systems.
Hourly temperatures for May, recorded at the AMRF Sentinel Car Park AWS show a few significant drops in average air temperature (see Figure 2). Earlier in the month, and on the 12th of May air temperatures approached freezing (0 oC) but did not drop below freezing. The freezing point threshold was reached at 08:00 on the 21st of May when air temperature dropped to -1.3 oC, marking the first subzero record for 2025 (see Figure 5). The freezing temperatures only lasted for two hours, and by 10:00 had returned to above freezing levels, but still an impressively cold 0.5 oC. Snowfall it seems was again spatially limited, falling mainly in the southern Drakensberg and in parts of Lesotho.
The observed evolution in air temperature over the Drakensberg during the progression of a cold front system highlights one of the many critical benefits of the AMRF network of weather stations. The stations not only provide near real-time insight into atmospheric dynamics, but over years a better understanding of our mountain climates can be developed. The northern Drakensberg stations initiated and maintained by AMRF and its partners at the University of the Free State and the University of KwaZulu-Natal should be the first step in a fully comprehensive network on stations across the Drakensberg mountains and Lesotho.
As winter progresses, we will keep an eye on the sky and the stations to identify further interesting developments.
