mixtemi. hazer ñublado. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 57r. col. 2. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
MIXTĒM(I) to be cloudy / está nublado [(4)Zp. 88,89,210]. Z treats this as a transitive verb and prefixes it with TLA-. See MIX-TLI, TĒM(I). Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 149.