Pokemon Go added the new feature, weather system, back in December 2017. This system affects how the Trainers interact with Pokemon, based on real-world weather conditions.
Certain types of wild Pokemon spawn more during specific types of weather. The fire-type Pokemon will appear during sunny days, while the water-type Pokemon will show up when it is raining outside. During matching weather conditions, these weather-boosted Pokemon can be quite difficult to catch than usual.
The weather-boosted Pokemon perform better in battle. They also have a higher CP and the best thing about them is that you get extra Stardust when caught. If you want to see how much power your Pokemon actually has, look for your team leader. The more your team leader is excited about your Pokemon, the better it is. If your he/she says that your Pokemon is “breathtaking,” “can really battle with the best,” or “it can accomplish anything”, then you know that you got a top-tier Pokemon.
The weather does not affect only the Pokemon you catch, but the ones you have already got have benefited from it too. If the weather you have is compatible with some type of attack that a selected Pokemon knows, for example, high winds and Air Slash, the attack will deal more damage.
Raid Battles are affected too. Let’s take the Legendary Pokemon Groudon for an example. As a Ground Type, it is quite weak to Water, Ice and Grass. When in a Raid Battle, we suggest you modify your strategy according to the weather. When clear, you should use Ground, Grass and Fire Type Pokemon (but be careful, Groudon gets weather boost). When rainy, you should use Water Type Pokemon. But don’t worry about Groudon, an army of Delibird can defeat this Legendary – easy!
For last, don’t forget about the weather bonus chart:
We do not recommend you to rely fully on the Pokemon Go weather system if you want to go outside. It isn’t as accurate as an app that is dedicated to weather forecast.