[f5fstop]

Were the tires cold (vehicle not driven for about 3 hours) when you filled the air?
If the tires were cold when pressure was increased to 35 psi, and it is 60 degrees, and it drops to 30 degrees tonight, the tire pressure should reduce to 32 psi. I don't believe this should set off the system warning.
From what I have seen it appears to be around 30 psi and lower.
If the tires were warm, the cold tire pressure might be actually around 33 psi.
Either way, 30 psi is low for a tire that is supposed to be inflated to 35 psi when the tire is cold. It also appears the system is operating correctly, if you added air and the sensor warning went away.

It is normal to have to adjust air pressures during times when the ambient air temperatures either drop or increase.