I use mortscript to control my backlight with a button, but it does have time commands that you could use.. also there are weather scripts designed for s2u2, but s2u2 is not required to use these scripts.
that actually sounds like a great idea, I've been meaning to revamp the weather script i've been using anyway.
this is the script I have assigned to my vc button.
Code:
SetBacklight( 10,10 )
Sleep( 60000 )
SetBacklight( 5,10 )