George Walter Cox entered the civil service of the Transvaal Colony in November 1902. In 1906, while residing in Johannesburg, he passed the matriculation examination of the University of the Cape of Good Hope as a private student. On 1 April 1913, following the formation of the Union of South Africa in 1910 and the amalgamation of the four colonial weather services in 1912, he was appointed as meteorological assistant at the headquarters of the Weather Service (in the Department of Irrigation) in Pretoria. There he remained for the rest of his career. He became a member of the South African Association for the Advancement of Science in 1916, serving as joint secretary of its Section A in 1926, and was elected a Fellow of the Royal Meteorological Society at some time before 1919. In 1931, when Mr C.M. Stewart* retired as Chief Meteorologist, Cox was appointed acting Chief Meteorologist until the appointment of Dr T.E.W. Schumann as Chief in September 1933.
From June 1918 Cox was mainly responsible for the first attempts in South Africa to measure wind direction and velocity in the upper air by means of pilot balloons. The balloons, released at first in Pretoria and later also at other centres, achieved a maximum height of 18 km. His early results were described in a brief article, "Notes on some upper air results in South Africa", in the Official Yearbook of the Union of South Africa. He reported further work in "Upper air research" (South African Irrigation Department Magazine, 1923), "Some notes on the circulation of the atmosphere over South Africa" (South African Journal of Science, 1926) and The circulation of the atmosphere over South Africa (Pretoria, Meteorological Memoir No. 1, 1935). In the latter publication he reported the resultant directions and velocities of winds at various heights for each month of the year, finding virtually no difference in the circulation between the summer and winter seasons.
Cox gave attention also to the measurement of precipitation and long-term weather forecasting. His results were reported in several papers, including "The intensity of rainfall in the Transvaal" (Report of the South African Association for the Advancement of Science, 1915); "Seasonal weather forecasts" (South African Journal of Science, 1923); and "Periodicity in rainfall" (Transactions of the Royal Society of South Africa, 1925).
Cox was married to Bessie Jeanette Keeling, with whom he had a son.