**4. Conclusions**

The Tmin and Tmax trends showed variation across the weather stations used in this study. For instance, the Tmin in Clocolan, showed a declining trend throughout the growing period between October and April, while in Marquard the minimum temperature increased between October and December. The maximum temperature was consistently increasing in all the stations except for Clocolan, where a decline was only reported for the month of March. The November and February trends are important for maize production that involves planting (leaf initiations, leaf and root growth) and development (tasseling and grain filling) of maize, respectively. The entire growing period (October–April) minimum and maximum temperatures for the period from 1985 to 2016, varied across the four different stations of the Setsoto municipality. The increasing minimum and maximum temperatures in all the stations of this study showed that: (1) where the minimum temperature is currently too low for optimal growth, an increase in these temperatures will increase yield and (2) the overall increase in both the minimum and maximum temperatures over time can negatively impact yield, but the magnitude of the effect is dependent on when exactly the increases are taking place during the growing season. November and February have been highlighted as specific times at which the crop is most at risk.

The changes in rainfall were significant only in Ficksburg in the month of January with a value of 2.34 mm year−<sup>1</sup> Nevertheless, the rainfall showed a strong positive correlation with yield (*r* 0.46, *p* ≤ 0.05). This study indicates that the rainfall variability is increasing in parts of the study area, which could be attributed to several global and regional rainfall phenomena. There were some periods where it did appear that the yield was below average, similarly, there were periods from 2006–2012, where the yield was above the average maize yield per hectare (2.42 tons ha<sup>−</sup>1). There are some concerns, especially in the Senekal area, that it will be no longer economically viable for maize production. Yield is not just a product of climatic variables, but also a combination of other agronomic factors. The average rate of increase of yield in the Setsoto Municipality is 0.044 tons ha−<sup>1</sup> per annum across the stations.

The strongest positive correlation (46–68%) with yield and rainfall was during the growing period in Clocolan. The changes in minimum temperature are having two different effects on the yield in the area where: if it is colder, the yield will be negatively impacted; if it is getting warmer, where the minimum temperature has previously limited yield, the yield will be positively impacted. Increasing maximum temperatures still shows no negative impacts on maize yield except for a single month of February in Marquard. Palmer drought stress indices should be explored further to help support more accurate forecasting. This study serves as an important baseline of the impacts of agroclimatic variables on maize yield at this local scale which is a key area of production. Farmers cannot make rapid decisions about farming practices, where to plant or whether to sell the land. This study contributes to raising awareness about the risk of ongoing maize production in this area.

**Author Contributions:** A.H.B., collected and analyzed the data and wrote the initial draft of the paper. M.S. and S.W.N. conceptualized the study and acted as supervisors of the postgraduate student, H.A. M.S. did a significant amount of reanalysis and interpretation of the data and writing of the manuscript. S.N. provided some data and did some checking of the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Prof Mary Scholes, who holds a Research Chair in Systems Analysis which is funded by the Department of Science and Innovation and the National Research Foundation in South Africa. The grant number is 101057.

**Conflicts of Interest:** The authors declare that there is no conflict of interest.
