The temperature dependence of the NO3 absorption spectrum was measured over the wavelength range 440-720 nm and temperature range 298-200 K using a diode array spectrometer. The NO3 absorption cross section at 662 nm, the peak of the 0-0 transition, was measured using time resolved tunable diode laser absorption following 351 nm laser photolysis of a Cl-2/ClONO2 mixture. The NO3 absorption cross section at 662 nm was (2.23 +/- 0.22) x 10(-17) cm(2) at 298 K and increased 36% in going from 298 to 200 K (2 sigma error limits including estimated systematic errors). These results are quantitatively compared with previous measurements.