NHTSA's Fatal Accident Reporting System (FARS) data files covering the period 1975 through 1982 are analyzed. Primary variables of interest are tractor-trailer fires, month of the year in which the accident occurred, and the state in which the accident occurred.

The incidence of tractor-trailer fires increases during the summer months throughout much of the U.S., and is higher than average in many southwestern states. The two factors, region of the country and season, are, in part, additive. This supports the premise that ambient temperature is an underlying contributing factor to these fires.