Lester Gaynor enlisted in the U.S. Army in 1939, and in 1941 he was transferred to Christmas Island with assistant Francis Wallis. He and Wallis established the first weather station on Christmas Island and transmitted radiosonde and hourly surface data to Hickam Field, Hawaii, located about 1400 miles to the north. He developed an interest in meteorology during WWII when he was in the Air Weather Service and supported combat air and ground operations in the central Pacific Ocean. After the war, Gaynor kept in touch with many of his wartime comrades, and organized 7th Weather Squadron reunions in San Francisco and Detroit. He studied the history of Christmas Island on travels around the world with his wife, Mildred.