Spectra of high-metallicity [12+log(O/H) >~ 8.2] HII regions, where oxygen auroral lines are measurable in both the O+ and O++ zones, have been extracted from the Data Release 6 of the Sloan Digital Sky Survey (SDSS). Our final sample consists of 181 SDSS spectra of HII regions in galaxies in the redshift range from ~0.025 to ~0.17. The t2,O-t3,O diagram is examined. In the SDSS HII regions, the electron temperature t2,O is found to have a large scatter at a given value of the electron temperature t3,O. The majority of the SDSS HII regions lie below the t2,O-t3,O relation derived for HII regions in nearby galaxies, i.e. the positions of the SDSS HII regions show a systematic shift towards lower t2,O temperatures or/and towards higher t3,O temperatures. The scatter and shift of the SDSS HII regions in the t2,O-t3,O diagram can be understood if they are composite nebulae excited by two or more ionizing sources of different temperatures.