Severe flooding in winter; it's possible
A number of news stories recently have contained one sentence to the effect of, "severe flooding in our area usually happens in spring." This statement is unequivocally factual. However, this should not be taken to mean that severe flooding cannot happen in other seasons, including fall, or even winter. Flooding is caused by there being too more water flowing into and through the river channel at a rate higher than is able to be moved downstream. Flooding of a severe nature in our region is most likely when it rains while a winter's worth of heavy snow melts while the ground is still frozen. Summer floods are the result of repeated heavy thunderstorms.
However, a serious flood, even a record flood, could happen in the fall or even in winter. Extraordinary weather is happening all the time around the world. With weather, the fact that a thing usually does not happen a certain way in our experience should not be taken as proof that it cannot happen.