The attack on Pearl Harbor occurred on December 7, 1941, and launched the nation’s entry into World War II. As the United States went to war, an executive order from then-President Franklin D. Roosevelt defined the role of the Weather Bureau and emphasized a more direct relationship between the bureau and the War Department.
Concerns regarding the distribution of weather information arose and by December 19, less than two weeks after the strike on Pearl Harbor, the Office of Censorship was established. Meteorological data between Washington and London had already been halted earlier in the war efforts for that reason, according to the National Weather Service. A series of actions by the Weather Bureau sought to prevent weather reports from falling into the wrong hands.
Hourly weather observations continued at airport stations, but access to observations was limited to Army and Navy representatives, pilots, and dispatchers for specific airlines. Weather reports for pilots were made in such a way as to relay only whether a flight could be completed. Observation reports and weather charts were kept out-of-sight and locked in drawers when no one was in the office. The distribution of weather information and forecasts to the public was limited to newspapers and telephone, as it was recognized that radio broadcasts could be intercepted.
A “Censorship Code” was issued by the Office of Censorship in Washington. This code applied to all newspapers and essentially limited forecasts, observations, and weather-related news stories to a 150-mile radius surrounding the publication city. The publication of sky conditions and exact temperature forecasts were not allowed, but general terms were permitted. Phrases such as “little change in temperature” or “much cooler” were accepted for publication. Wind forecasts generally excluded wind direction and contained vague descriptions of speed. The mention of heavy snow was considered “an aid to saboteurs” and was thus not permitted.
In March 1942, a devastating tornado outbreak ripped through the Central and Southern United States. The censorship of weather data during the two-day tornado outbreak prohibited the radio from broadcasting any information. It remains one of the deadliest tornado outbreaks in United States history, with more than 150 casualties and nearly 13-hundred injuries. The following year, in October 1943, restrictions were eased and by 1945, they were eliminated following the end of the war.