Visibility Ranges

Visibility Ranges

The procedure for making personal observation to determine the forest fire smoke index value for local areas without National Weather Station (NWS) or Department of Environmental Quality (DEQ) monitors is:

  1. Face away from the sun.
  2. Determine the limit of your visible range by looking for targets at known distances (miles).
  3. Visible range is that point at which even high contrast objects totally disappear.
  4. Use the values below to determine the local forest fire smoke category.
Health Effects Categories Visibility Ranges (miles)3
Hazardous Less than 1.3
Very Unhealthy 2.1 - 1.3
Unhealthy 5.0 - 2.2
Unhealthy for Sensitive Groups 8.7 - 5.1
Moderate 13.3 - 8.8
Good 13.4 +