Monthly mean of diurnal (daily) temperature ranges for the 50 year (1950 - 1999) period (C) - March

The diurnal temperature range is the difference between the maximum and minimum temperatures on a given day. Some plants respond to the rhythmic variations brought about by shifts from high temperatures during the day to low temperatures during the night. The main long term factors affecting diurnal temperature ranges over South Africa are continentality and altitude (Schulze, 1997). It nevertheless needs emphasising here that short term, irregular diurnal conditions are often controlled by the passage of cold fronts or other air masses which may be associated with strongly contrasting temperature regimes. "Monthly means of diurnal (daily) temperature ranges were derived from the 50 year (1950 - 1999) time series of quality controlled daily maximum and minimum temperature values generated at each of the 429 700 one arc minute (i.e.1.7 x 1.7 km) raster points covering South Africa, using the regional/seasonal lapse rate and infilling techniques developed by Schulze and Maharaj (2004). From theoretical considerations, experience and analyses of high quality daily temperature datasets, the diurnal temperature range is very seldom < 2 degree Celsius. When, therefore, on a given day the temperature range value was computed to be < 1.5 degree Celsius, this value was `forced` to be 1.5 degree Celsius, with equal compensatory adjustments being made to that day's maximum and minimum temperature values."

日温度较差（diurnal temperature range）指某一观测日内最高气温与最低气温的差值。部分植物会响应因日间高温向夜间低温转变所引发的节律性温度波动。影响南非地区日温度较差长期变化的主要因子为大陆性与海拔高度（Schulze, 1997）。但在此需着重强调：短期、不规则的日间温度条件往往受冷锋过境或其他气团活动控制，此类气团通常伴随显著迥异的温度格局。
本数据集的日（逐日）温度较差月均值，源自覆盖南非全境的429700个1弧分（即1.7×1.7 km）栅格点（raster points）的50年（1950-1999年）经过质量控制的逐日最高、最低气温时序序列，采用Schulze与Maharaj（2004）开发的区域/季节气温递减率及插补（infilling）技术计算得到。基于理论推导、实践经验与高质量逐日气温数据集的分析结论，日温度极差极少低于2摄氏度。因此，当某日的温度极差计算值小于1.5摄氏度时，该值将被强制修正为1.5摄氏度，并对当日的最高、最低气温值进行等量的补偿调整。