Radar observations of wild fire plumes in Oklahoma carried out with the prototype of dual polarization S-band WSR-88D (KOUN) weather radar are presented. KOUN data is compared with data from operational single polarized WSR-88Ds. To enhance detectability of plume smokes, different options of radar signal processing are discussed. The observations show that the copolar correlation coefficients between horizontally and vertically polarized returns in the plumes are mostly less than 0.4. No other natural scatterers have such low values and this can be used in identification of plumes. An explanation for low correlation coefficients in smoke is offered.