He charted new Pan American Airways air routes throughout the Asia Pacific region in the era before weather satellites and computer-generated instant data.
A photographer of nature and atmospheric phenomenon, he published numerous books, articles, atlases and cloud charts that explained the importance of weather.
Learning that the Boeing School of Aeronautics in Oakland, California guaranteed its graduates a job in the new field of commercial aviation, he joined Boeing's first class in the emerging field of Aviation Weather Forecasting and then went to work for Pan Am World Airways, helping chart new air routes throughout the Pacific region for the four-engine "California Clipper" flying boats.
Day was responsible for providing accurate advance notice of inclement weather such as a rogue hurricane/typhoon or South Pacific cyclone along the 2000-mile over-water routes, ensuring passenger comfort and safety.
In 1946, Pan Am sent him from Manila to Tokyo to provide forecasting services for the transport of UNRRA (United Nations Relief and Rehabilitation Administration) personnel from the U.S to China.
[1] In 1946, Day left Pan Am to begin an academic career teaching physics at Oregon State College (OSC).
After earning his Ph.D in cloud physics from OSC in 1956, he taught at the University of Redlands in California from 1956 to 1958, then returned to Oregon to teach atmospheric sciences at Linfield College in McMinnville.
[4] He authored a total of eight meteorological, climate and environmental textbooks starting with Water, the Mirror of Science,[5] (1961, with Kenneth Davis) and most recently in 2002, The Book of Clouds,[6] which featured the best of his photography and easy-to-understand explanations of weather phenomena.
In the 1970s, acting as "The Cloudman", he wrote a weekly column, "Words on the Weather", for the McMinnville, Oregon News-Register newspaper, that appeared in over 1000 installments from 1978 to 2007.