Niantic has announced a huge Pokemon GO update set to arrive later this week. The update will add a dynamic weather system and 50 new Pokemon originally seen in the third generation games, Pokemon Ruby and Pokemon Sapphire.

The 50-Pokemon lineup includes starters Treecko, Torchic, and Mudkip. The announcement trailer also confirms Salamence, Shiftry, Aggron, Ludicolo, and Groudon. Naturally, the pre-evolution of the former four Pokemon are also included - e.g. Bagon and Shelgon for Salamence and Aron and Lairon for Aggron.

More than just a visual touch-up, the new dynamic weather system will have a significant effect on the gameplay. The system will reflect the local weather conditions in the game and change the behavior of certain Pokemon types in the wild.

For example, Water Pokemon will appear more often when it's raining and Ice Pokemon will run around more frequently when there's snow. Furthermore, the system will boost the power of certain attacks based on the weather condition. For example, a Fire Spin from Charizard will hurt a lot more when used during sunny days.

Niantic did not give a specific date on when the big update will arrive. But the developer did tease that more new Pokemon will appear over the next several weeks after the first batch.