The National Fire Danger Rating System ( NFDRS) was developed nearly 40 years ago for use by wildland fire fighting agencies throughout North America. Modifications to the original system were made over several decades and now used by firefighters worldwide. NFDRS is a collection of important 24 hour forecasts, based on complex equations, where easily collected field data from thousands of regional weather stations assess various fuel, weather, topography and risk conditions.
The system not only is easy to use but is also reasonably inexpensive to operate and portable stations can be used. The most relevant outputs are expressed in simple terms which are easily understood and collected by users. The data is ultimately classified into 5 classes and the class number is increased as fire danger conditions increase. You see these Smokey Bear signs at many fire protection stations and on State and National Forests and Parks.