Compound Hot‐Dry Days ( <scp>CHDDs</scp> ) and Their Implications on Maize Yields in the Free State Province, South Africa

ABSTRACT Compound occurrence of extreme weather events and their impacts on agriculture have been widely investigated in many regions except for South Africa. This study explores the variability of compound hot‐dry days (CHDDs) using daily rainfall and temperature data from 1950 to 2023 in the Free State Province. Their trends over time are determined for different 30‐year periods starting in 1950. The effect of El Niño Southern Oscillation (ENSO) on the CHDDs was also investigated. To determine the impact of extreme events on food security, the study evaluated an association between CHDDs and maize yields. The results show significant ( p &lt; 0.05) increasing trends in CHDDs. 30‐year period trends starting in 1950 were mostly not significant ( p &lt; 0.05) except for isolated cases in Bloemfontein and Bothaville. Correlations between CHDDs and Oceanic Niño Index showed significant ( p &lt; 0.01) positive Pearson correlation. Generally, during El Niño years, the frequency of CHDDs was high in all the stations with the maximum exceeding 140 CHDDs obtained in the 2015/16 season. In contrast, most of the years in which the frequency of CHDDs was below 40 occurred in La Niña years. In addition, CHDDs had a significant ( p &lt; 0.01) negative correlation with yield anomalies. The results also showed extremely high negative yield anomalies during El Niño years, while most of the years of extremely high positive yield anomalies occurred in neutral years. The results clearly show linkages between ENSO and CHDDs increasing the likelihood of a reasonable forecast of seasonal CHDDs especially in South Africa where the past results have shown high predictability of the ENSO index. The significant association of CHDDs with maize yields is a factor that can be helpful in projecting the scale of food security and level of international commodity trade for the country. The agricultural sector needs to improve agricultural systems resilience against compound extreme weather events across several commodities.