[2] After retiring as a faculty member at CSU in 2005, Gray remained actively involved in both climate change and tropical cyclone research until his death.

[3] Upon returning to the United States in 1957, he began work as a research assistant at the University of Chicago Department of Meteorology from 1957 to 1961.

One of them was Remember Up-Moist, Down-Dry and Keep it Holy which was the reference to his conviction that one has to include moisture processes such as evaporation and rainfall to understand atmospheric energy balance.

On 1 October 1954, Gray married Nancy Price and they had four children together: Sarah, Anne (deceased), Janet, and Robert.

[10] In the late 1970s, Gray noticed a trend of low hurricane activity in the North Atlantic basin during El Niño years.

He found numerous factors across the globe influence tropical cyclone activity, such as connecting wet periods over the African Sahel to an increase in major hurricane landfalls along the United States East Coast.

[8] Students and colleagues joined his forecast team in the following years, including Christopher Landsea, Paul W. Mielke Jr., and Kenneth J.

[1] After the 2005 Atlantic hurricane season, Gray announced that he was stepping back from the primary authorship of CSU's tropical cyclone probability forecasts, passing the role to Philip J. Klotzbach.

[18] Although he agreed that global warming was taking place, he argued that humans were only responsible for a tiny portion and it was largely part of the Earth's natural cycle.

[16][18] In June 2011, Gray wrote a paper directed at the American Meteorological Society, opposing their embrace of anthropogenic global warming.

[19] Peter Webster, a Georgia Institute of Technology professor, was part of the anonymous peer review on several of Gray's National Science Foundation proposals.