Tropical cyclones typically drop large amounts of rain along and near the storm's path. The slower and more significant the storm’s size, the higher the likelihood of higher rainfall totals. Some storms can drop well over 30 inches of rainfall, like when Hurricane Harvey dropped over 60 inches near Nederland, Texas, in 2017.

Tropical Storm Chantal might have had the perfect recipe for catching people unawares: It formed rapidly (only reaching tropical storm status on Saturday) over a holiday weekend and moved slowly while dropping torrential rain.