Well, people do actually buy separate "clock-weather-thingys" which show the temp, weather etc, so considering the sensor(s) probably don't cost much, adding it to the tablet can have its uses for similar purposes as those.
And it could actually give quite unique features for games too - think about the possibility of having a game where weather is actually dynamic and based on the weather of your actual location?
You start playing on some sunny day, in a sunny game, and suddenly a thunderstorm appears not only in real life, but in the game too?
Or you play at winter, and it's winter in the game too?
Littlest things can do miracles