1. Research Unit, Foundation for Professional Development, Pretoria, South Africa
2. Department of Mathematics and Applied Mathematics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
3. Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, California, USA
4. South African Weather Service, Private Bag X097, Pretoria 0001, South Africa
5. School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
6. Department of Mathematics, Vaal University of Technology, X021, Vanderbijlpark 1900, South Africa
7. Department of Statistics, Federal University of Technology, P.M.B 704, Akure, Nigeria
8. Department of Geography, Geoinformation and Meteorology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa