September 1 is Bōsai no hi, Disaster Prevention Day. It was established in 1960. The date is the anniversary of the Great Kantō Earthquake of 1923. It also falls near nihyaku tōka, the 210th day counted from the start of spring in the traditional calendar, a time known for typhoons.
Since a cabinet understanding of 1982, the week around September 1 has been Disaster Prevention Week. The government calls for disaster drills during that week.