Joystiq
Joystiq News
is getting a slew of new Pokémon this week as well as a dynamic weather system later this month. The game will soon reflect the real weather around you and that will affect which Pokémon you see and how strong they are. If it's raining, for example, you'll see more water-type Pokémon than usual and they'll start out with a higher CP than they typically would.
Source:
Console Bang News!