While the father and sons are at the dump a natural disaster occurs when a strong lightening occurs followed by a thunderstorm.
What natural disaster happens?
When the father and the son were at a dump in the short story, "Distillation," we learn of the series of lightening and thunderstorms that followed. The sky turned black and the wind howled as the duo were leaving the dump.
There was also a large crash and a lightning flash that happened at the same time. While the narrator was terrified, his father was calm and tried to also help him remain calm.