The wet weather could disrupt Halloween festivities for millions of Americans, particularly in the West, Midwest, and Southeast. Southern Alabama, Georgia, Louisiana, and Florida are likely to experience widespread showers, with localized areas at risk of flash flooding. A Level 1 out of 4 flash flood threat has been issued for Louisiana, southern Georgia, and Mississippi. Coastal areas, including San Francisco, may face additional risks due to a Coastal Flood Advisory. The rain could also lead to hazardous driving conditions and localized flooding in low-lying areas.