Unstable atmospheric conditions caused by cold air are bringing intense rainfall to eastern Japan, particularly the Kanto region. Meteorological authorities report rapid development of rain clouds and are warning of potential low-lying flooding and rapidly rising river levels. Residents are urged to be vigilant against hazards including lightning strikes, possible tornadoes, and hail. The affected areas are experiencing significantly unstable weather patterns. Authorities advise caution and preparedness due to the potential for localized, severe weather events. The situation is being closely monitored as the unstable conditions persist. These conditions are impacting both northern and eastern Japan.