Dense Fog in the United States

How dangerous are Dense Fog events in the U.S.?

Human impact is a defining part of this hazard's NOAA record. Across 7,664 events, the database lists 135 fatalities and 450 injuries. PlainHazard places hazard types with at least 100 recorded fatalities in its very-high human-toll band. That is a descriptive grouping of this 2015-2025 catalog, not an official NOAA risk grade and not a statement about the severity of every individual event.

Geographic exposure is heavily concentrated in a handful of high-severity states. The three states absorbing the largest share of events are California (1,605 events, 52 fatalities), Illinois (1,122 events, 5 fatalities), Kentucky (1,006 events, 1 fatalities), reflecting both physical geography (coastal exposure, plains corridors, terrain) and dense population sitting directly in harm's way. At the other end, states such as South Carolina, Oklahoma, Nebraska report far fewer events, a genuinely rare event outside the leading states, not merely an underreported one.

This is a more frequency-heavy than loss-heavy record. The hazard ranks #17 by event count but #30 for combined property and crop damage, a gap of 13 places. Its listed losses represent <0.1% of the catalog total. The human-toll rank is #17, or 1.3% of recorded fatalities, so neither event count nor damage rank substitutes for the other.

The year-to-year record shows real volatility around a high baseline. The peak year on record was 2020, logging 1,002 events and $263.0K in property damage in a single calendar year. The most recent year in the dataset is 2025 with 632 events recorded. Across the full 11-year window, annual event counts reflect seasonal climate cycles (ENSO phases, active vs. quiet severe-weather years) and long-term shifts tied to a warming climate both help explain the swings.

Frequency and per-event lethality sit close together for this hazard: #17 by event count and #19 by fatalities per event among the 44 types with at least 100 recorded events, at 17.6 deaths per 1,000 recorded events. Recorded damage averages $1.8K per event. Neither the cumulative total nor the rate is misleading here -- they tell the same story.

NOAA entries are reports filed by local National Weather Service offices. Counts therefore reflect both observed weather and reporting practice; they do not measure unreported events, household exposure, or the probability of a future event at one address.