The prevalence and median intensity of infection of Pacific sierra (Scomberomorus sierra) by parasitic copepods (Caligus fajerae, Caligus omissus, and Cybicola buccatus), and monogeneans (Thoracocotylidae) were examined over a six-year period (2015 to 2021) in the southeastern Gulf of California. This period included sea surface temperatures that were warmer and colder than average (SST anomalies). A regression model indicated that the prevalence of parasitic species was higher when conditions were warmer than average, although some of the relationships were non-significant. Prolonged periods of high temperature and heat pulses >2 °C above the average temperature negatively affected the prevalence of parasites. A moderate or high prevalence of parasites was observed during colder than average conditions. These results are in accordance with those of previous studies showing that fish ectoparasites are able to develop under a wide range of thermal conditions.