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Dense Fog / Smoke Threat

The "Dense Fog/Smoke Hazard Map" depicts the local threat of dense fog or smoke for specified areas.  It is largely based on coverage and visibility.

Dense Fog/Smoke Threat Level

Threat  Level Descriptions

Extreme

"An Extreme Threat to Life and Property from Dense Fog or Smoke."

Widespread very dense fog or smoke with the predominate visibility near zero and the  coverage greater than 55% within a defined area, persisting for at least 1 hour.

High

"A High Threat to Life and Property from Dense Fog or Smoke."

Areas of very dense fog or smoke with the visibility near zero and the coverage 25 - 54% within a defined area, persisting for at least 1 hour. 

Moderate

"A Moderate Threat to Life and Property from Dense Fog or Smoke."

Widespread dense fog or smoke with the predominate visibility 1/8 - 1/4 mile and the coverage greater than 55% within a defined area, persisting for at least 1 hour...OR...patchy very dense fog or smoke with the visibility near zero and the coverage less than 25% within a defined area, persisting for at least 1 hour.  Surrounding fog may or may not be present. 

Low

"A Low Threat to Life and Property from Dense Fog or Smoke."

Areas of dense fog or smoke with the visibility 1/8 - 1/4 mile and the coverage 25 - 54%  within a defined area, persisting for at least 1 hour.  

Very Low
" A Very Low Threat to Life and Property from Dense Fog or Smoke."

Patchy dense fog or smoke with the visibility 1/8 - 1/4 mile and the coverage less than 25% within a defined area, persisting for at least 1 hour.

Non-Threatening
" No Discernable Threat to Life and Property from Dense Fog or Smoke."

Visibility greater than 1/4 mile and non-threatening.  Fog/smoke may still be present, but not dense.  

Note: Fog or smoke becomes hazardous when it is considered "dense" and obscures visibility to 1/4 mile or less.  This results in decreased response time for operators of motor vehicles, especially at higher speeds.  Motorists should adjust driving speed accordingly, while using low-beam headlights.