On May 30, 1917, Drewry Hubert Bagley was born in Forsyth County, Georgia, just outside of the town of Cumming. He was one of eight children born to Harl William Bagley. H.D.'s mother, Cora Holman Bagley, had seven of these children. Harl's first wife, who gave birth to his first son, died at a very young age. Among the seven siblings, H.D. had four brothers - Rick, Herbert, Hollis, and Harold, and three sisters - Hazel, Helen, and Winnie. The whole bunch helped keep things going at the farm they lived on.

It was the event of April 6, 1936 that may have first sparked H.D.'s real interest in weather. On that day, Gainesville, Georgia was the target of an F4 tornado. The tornado hit a school in the town, killing over 200 students. An additional 1600 were injured. H.D. traveled to Gainesville to witness the destruction first hand. It was an experience he would not soon forget.

Back at home, money was scarce during this time as H.D. grew up in the midst the Great Depression. Jobs were also scarce and to make matters worse, the crops they grew were not worth much money. So, the kids had to look for other jobs. In March 1933, then President Franklin D. Roosevelt began the first "New Deal" project, the Civilian Conservation Corps (commonly referred to as the CCC). The CCC provided jobs to many Americans, and became an important part of economic recovery in the country. H.D. got his first big break with a CCC job in July 1936 in the Chattahoochee National Forest at Robertstown, Georgia, a small town in the northeast part of the state. His job was to build fire roads and bridges through the forest, some of which are still used today. In October 1936, the Robertstown Camp closed and H.D. was transferred to the Buford Camp. Here, he worked for the Soil Conservation Service and helped plant trees and other plants to stop the erosion of ex-farmland. Within a year, at the age of 20, he began to hear the call to serve his country.