Kai persons dominate the glyphs in Thursday:

Hb9-39	Hb9-40	Hb9-41	Hb9-42	Hb9-43
Hb9-44	Hb9-45	Hb9-46	Hb9-47

In Thursday new fire is ignited, we can read from the kava signs (Hb9-43 and Hb9-45). It stands to reason because Thursday is the day of Jupiter, the wielder of thunder bolts.

It is also the 5th ('fire') day of the week. Though with thunder comes rain.