Dense Fog

Hazard in Severe Weather

A transportation-safety hazard — near-zero visibility behind chain-reaction crashes on highways, runways and waterways.

Plans also call it: fog, freezing fog

Talk to us about Dense FogAll 73 hazards →

What you’d hand your council

The first page of a Dense Fog evidence brief: likelihood, impact and readiness on your own scale, every figure sourced.

Evidence brief for Cedar Ridge County (example)

September 14, 2026

Dense Fog

Hazard in Severe Weather, on the established threats & hazards list

Impact
5432112345

Likelihood

Likelihood
2

Unlikely — Possible but infrequent — roughly once in 50 to 100 years (1–2% chance in any year).

Impact
2

Minor — Limited effects — few injuries, damage confined to a small area, brief localized disruption of services.

Readiness
4

High — The organization has a well-developed capability to manage this threat or hazard. Plans, personnel, resources, and skills are largely in place, and the capability has been meaningfully tested or demonstrated. Remaining gaps are unlikely to significantly impair performance.

  • 2source documents
  • 58verified mentions
  • —federal declarations
  • —NRI risk score
Worked example: Cedar Ridge County is fictional. The scores illustrate the format and are nobody's decision. Open a full sample brief →

The national record

FEMA’s National Risk Index doesn’t model Dense Fog. Your team fills it with local evidence, and Hazzard shows the gap rather than a zero.

How it maps

The same hazard in the vocabularies your plan and FEMA already use.

FEMA National Risk Index
Not covered
FEMA declaration incident type
Not covered
NOAA Storm Events type
Dense Fog, Freezing Fog
Hazzard category
Severe Weather, natural hazards

The national record

What the federal data says about Dense Fog: nothing yet

No federal dataset scores Dense Fog or files declarations under it. That's common for threats and emerging hazards, and it's why a brief for Dense Fog is built from your own plans, exercises and records. Hazzard shows the gap instead of inventing a number.

In your plan

What a Dense Fog profile needs, and where each part comes from

A local hazard mitigation plan profiles each hazard the same way (44 CFR 201.6). Here is how Hazzard fills each part for Dense Fog.

  1. Location

    44 CFR 201.6(c)(2)(i)

    Your documents

    No national layer maps Dense Fog. We draw the geographic extent from your plans, studies and annexes, cited to the page.

  2. Extent

    44 CFR 201.6(c)(2)(i)

    Your documents

    The magnitude your plans use for Dense Fog (a scale, a depth, an acreage, a duration), read from your documents and cited, so the profile states the strength you plan for.

  3. Previous occurrences

    44 CFR 201.6(c)(2)(i)

    Your documents

    FEMA files no declaration type for Dense Fog. The history comes from your after-action reports, incident records and plans.

  4. Probability of future events

    44 CFR 201.6(c)(2)(i)

    Your team decides

    No national dataset gives a frequency for Dense Fog. Your team scores likelihood on your scale from the evidence we organize.

  5. Vulnerability and impacts

    44 CFR 201.6(c)(2)(ii)

    Your documents

    The Census population profile and HHS emPOWER counts for context; the consequences themselves come from your plans and exercises.

  6. The assessment itself

    Your team decides

    Likelihood, impact and readiness for Dense Fog are drafted with every source attached, and a person on your team accepts each one. Hazzard never records a score on its own.

How we can help

How we’d help you prepare for Dense Fog

  1. 1

    We pull your county's record

    FEMA's National Risk Index rating and expected loss, every disaster declaration, and the daily temperature record behind heat and cold, before we meet.

  2. 2

    We read the plans you already have

    Your hazard mitigation plan and EOP annexes, so you can see what they say about Dense Fog and where the profile stops short.

  3. 3

    You leave with a cited brief

    Likelihood, impact and readiness for Dense Fog on your own scale, every figure tied to its source, ready for the planning team or the council.

Also in Severe Weather

Preparing for Dense Fog

Walk into your next plan update with Dense Fog already sourced.

Severe weather is the part of a plan everyone assumes is covered. We check whether yours says why, with your county's own record instead of a regional average. A person replies within one business day.

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