How weather influenced the atomic bombings of Hiroshima and Nagasaki

On this day in weather history, an atomic bomb was dropped on Nagasaki, Japan.

This Day In Weather History is a daily podcast by Chris Mei from The Weather Network, featuring stories about people, communities and events and how weather impacted them.


On Thursday, August 9, 1945, an atomic bomb devastated Nagasaki, Japan, three days after Hiroshima was destroyed the same way. The two bombings killed between 129,000 and 226,000 people, most of whom were civilians. This was an effort from the Allies to invade Japan during the final year of World War II. Weather conditions were a factor in these bombings. It needed to be a clear day so visibility was strong and photography opportunities were plenty.

On July 25, 1945, General Thomas Handy provided orders for the attack to General Carl Spaatz, the Guam-based commander of US Army Strategic Air Forces. The order said, "The 509th Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki."

Courtesy US National Archives

Courtesy of US National Archives

Further specifying, "To carry military and civilian scientific personnel from the War Department to observe and record the effects of the explosion of the bomb, additional aircraft will accompany the airplane carrying the bomb. The observing planes will stay several miles distant from the point of impact of the bomb."

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On Aug. 6, at 8:15 a.m., the 393d Bombardment Squadron B-29 Enola Gay dropped an atomic bomb called "Little Boy" on Hiroshima. The Japanese city was the primary target with Kokura and Nagasaki as backups. Another plane followed, later names Necessary Evil, to photograph the event.

There was a crosswind that caused the bomb to miss the exact target, the Aioi Bridge, and land around 240 m away on Shima Surgical Clinic. Little Boy killed between 90,000 and 146,000 people.

Japan still didn't surrender, so the officials met in Guam to discuss the next move. The plan was to drop another bomb on Aug. 11, but the weather wasn't clear. The forecast was clear on Aug. 9, so the bombing was rescheduled for that date.

On Aug 9, Bockscar, a United States Army Air Forces B-29 bomber, piloted by the 393d Bombardment Squadron's commander, Major Charles W. Sweeney, headed to Kokura to drop the atomic bomb.

Nagasaki mission crew

"The Bockscar and its crew, who dropped a Fat Man atomic bomb on Nagasaki." Courtesy of Wikipedia

The weather conditions in Kokura were poor, which ultimately saved the area. The Bockscar crew couldn't see Kokura well so they set out to another target. The bomber was running low on fuel, so the crew decided to head 160 km south to Nagasaki.

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Nagasaki was also overcast, but at 11:01, the was a break in the clouds. Bockscar's bombardier, Captain Kermit Beahan, saw the target and dropped the bomb. The bomb, named "Fat Man", detonated at 11:02, killing between 39,000 and 80,000 people.

To learn more about how weather impacted the Japan bombing, listen to today's episode of "This Day In Weather History."

This Day In Weather History is a daily podcast by The Weather Network that features unique and informative stories from host Chris Mei.

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