3.4.1. Minimum and Maximum Temperature Trends

The Clocolan monthly and the growing period minimum temperatures showed a negative trend at the 0.001 significance except in the months of November and April which showed a negative trend at a significance level of 0.05. The values of the Sen's slope were all less than zero (Table 5). In Senekal the Tmin did not show any trend for the period of the study except for the month of January, where an increase of 0.02 ◦C year−<sup>1</sup> was reported, compared to the increasing trend of 0.05 ◦C per annum shown in Ficksburg at a significance level of 0.05. In Marquard the Tmin trend showed a positive trend for the months of October, November and December at the rates of 0.09, 0.09 and 0.06 ◦C increase year<sup>−</sup>1, respectively during the growing period (0.01 significance level). The February, March, April and the growing period trends were negative with decreases of minimum temperatures of 0.1, 0.2, 0.25 and 0.05 ◦C year−<sup>1</sup> (Table 5).

**Table 5.** Setsoto monthly growing period minimum temperature annual trends during the growing period from 1985–2016. Mann Kendall (MK) trend (Test Z) and Sen's slope estimate (Q).


NB: \*\*\* denotes significance when alpha = 0.001, \*\* denote significance when alpha = 0.01 and \* denote significance when alpha = 0.05.

A commonly occurring pattern in climate change studies shows minimum temperatures to be increasing globally and more particularly in Sub-Saharan Africa [53]. The trends were very variable, all stations showing increases, except Clocolan which showed an overall decrease. The projected mid-altitude minimum temperature increases for subtropical Africa is 2.6 ◦C century−<sup>1</sup> [54]. The data were very variable by the month and in Marquard, there is a significant increase in the trend of Tmin in the months of October, November and December, likewise in January in Senekal and Ficksburg. These data are very difficult to explain. It is interesting to note that, Tmin spatial–temporal variability is just outside the WMO 30 km radius used for justification of infilling of data. There are local factors such as vegetation cover, topography, slope and aspect of the area which affect the rainfall and temperature distribution. The IPCC (2014), states that provided the anthropogenic and greenhouse emissions remain at 2014 levels, these results fall within the projected century temperature increases of 3 ◦C, but only for extreme events [54].

In the months of October and November in Marquard, Senekal and Ficksburg the growing period Tmax showed an increasing trend ranging from 0.04 to 0.10 ◦C year−<sup>1</sup> at various levels of significance (Table 6). In Clocolan, Tmax showed a decreasing trend in the months of March and April by 0.16 and 0.14 ◦C year−<sup>1</sup> (0.05 significance level).


**Table 6.** Monthly Maximum Temperature (◦C) annual trends during the growing period for the study period from 1985–2016. Mann Kendall MK Test Z denote Mann Kendall trend analysis test, and Q denotes 'the Sen's slope estimate' for the Setsoto municipality.

NB: + denote significance when alpha = 0.1, \*\*\* denote significance when alpha = 0.001, \*\* denote significance when alpha = 0.01 and \* denote significance when alpha = 0.05.

The maximum temperatures over most of SSA are expected to increase above the global average [55]. The increasing trend of maximum temperature for Southern Africa is non-linear and its intensity is expected to increase drought and crop failure [14]. In this study, the maximum temperatures in the period between 1985 and 2016 showed an overall significant increase, during the maize growing period across the stations in the Setsoto municipality. The only months with significant decreases in Tmax were March and April in Clocolan, while for the rest of the months either it remained unchanged or showed a significant increase (Table 6). The annual maximum temperatures increased by 0.08 ◦C year<sup>−</sup>1, giving an increase of 2.56 ◦C for the entire study period of 32 years. These results also agree with the findings published by the IPCC (2014). The results also fall within the projected SSA temperature increases of 6.5 ◦C for the century [55–58].
