Properties of phosphorus-doped crystalline silicon wafers were characterized as a function of temperature using terahertz time-domain spectroscopy (THz-TDS) in reflection. Four wafer samples of various resistivities from about 0.4 to 50 Ωcm were characterized from 300 K to 475 K, and the high frequency characterization over this temperature range is novel. Scattering times were predicted and measured on the same order of magnitude, and the anticipated reduction of scattering time with increasing temperature was observed. Absorptivity was estimated and measured as a function of frequency up to 1 THz with good correlation. Measurements confirmed that Drude’s theory is adequate to model silicon dispersion at high temperature.