According to Eurogamer Sega's upcoming NiGHTS: Journey of Dreams will link in with the Wii weather channel.
This means that if it's shining outside then it will be nice and sunny in the "A-Life" mode which lets you create your own sandbox adventures. Characters in the game will also change based on the time of the day and what the weather is.
NiGHTS: Journey of Dreams is exclusive to the Wii and looks like it is going to take full advantage of the Wii. The game will make use of WiiConnect 24 and also be playable with several different controllers.