Statistics are presented covering 20 years of use of the 2.1m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, Baja California, Mexico. As in the previous compilation, the fractional number of nights with totally clear, partially clear and mostly cloudy skies were determined. The fraction of nights lost due to bad weather was 22.2% in the period July 1982 to December 2002. From January 1984 to December 2002, 63.1% of the nights were of ``photometric'' quality and 80.8% were of ``spectroscopic'' quality. During the past seven years of ``drought'' in the area, the fraction of photometric quality nights increased to 73.5%, but the fraction of spectroscopic nights remained similar to previous years. The figures are similar to those reported for the Chilean sites and are better than those for Northern Hemisphere observatories.