Daily atmospheric measurements of spectral Aerosol Optical Thickness (AOT), precipitable water vapor (W), and irradiance were being carried out (ISRO-RESPOND Project) at Mysore, India (12.3oN), a continental station, on the day a massive tsunami struck India’s coast, December 26, 2004. A comparison was made of that day’s data with two other days: December 25, 2004, the day before tsunami and December 27, 2004, the day after. Compared to the values of AOT on December 25, 2004 and December 27, 2004, AOTs on December 26, 2004 were very low throughout the day. Values were almost one-third the magnitude of the other two days. The values measured on December 26, 2004 are unique because no other day in this month showed such low values. Comparison of the results with some other location is not possible at this point, because there appears to be no other study of this kind to support the observed results. Possible conclusions are drawn based on the available information.