pixahui.

Headword: 
pixahui.
Principal English Translation: 

to mist, to sprinkle, or for snow to fall (see Molina)

Orthographic Variants: 
pixaui
IPAspelling: 
piʃɑwi
Alonso de Molina: 

pixaui. (pret. opixauh.) lo mismo es que pipixaui.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 82v. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

pixaui (verb) = to snow, to rain
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1877), 160.

In icoac tepeticpac moloni, momoloca, motlatlalia, mopiloa: mitoaia, ca ie uitze in tlaloque, ie quiiauiz, ie pixauizque in aoaque. = When clouds billowed and formed thunderheads, and settled and hung about the mountain tops, it was said: “The Tlalocs are already coming.
Now it will rain. Now the masters of the rain will sprinkle water."
Todd Olson, "Clouds and Rain," Representations 104:1 (Fall 2008), 102–115; quote, from the Florentine Codex, appears on 102.