Relatively few studies have been performed about the onset, duration, and intensity of the canícula (midsummer drought) within central México in response to El Niño/Southern Oscillation (ENSO) events. The objective of our research is to assess the impact of the El Niño (EN) phase of ENSO upon air temperature (T), precipitation (PP), and drought index (DI = PP/T) during the canícula period. Daily air temperature and precipitation data from weather stations throughout central México are averaged for eight consecutive 10 (or 11)-day periods during the summers of 1960 through 1998. The data are grouped into seven climate regions according to specific precipitation criteria. Statistical comparisons between EN and neutral (N) years for the seven regions are made with pooled average T, PP and DI values from the summer. Results indicate that the EN phase significantly increases air temperatures within the wetter climate regions. The El Niño phase also increases summer precipitation within five of the regions, though not significantly. The added summer rainfall during El Niño phase does not reduce drought intensity with the exception of brief intervals within the wetter regions. Roughly, during EN and N years the canicula begins on July 11 and ends on August 31.