With the release of generation 3 in December 2017 dynamic weather effects were introduced. The current weather is displayed in the bottom right corner of the map. There are seven weather conditions, that boost different Pokémon type’s (see Table 18) spawns and combat abilities. The weather condition updates every full hour (source).
- Increased spawn rate
- 25 % extra Stardust for successful catches
- Increased maximum level for catching (35 wild, 25 raid bosses)
- Increased minimum IVs for wild catches (apparently 4)
It is definitely worth it to go out and hunt strategically with the weather. For example, magikarps will be a good target during rainy weather. The saved Stardust of a level 35 catch compared to a level 20 catch is huge (150,000). Even when the level 35 Pokémon has only average Ivs it will be pprox.. as strong as a level 30 Pokémon with high Ivs. It has never been easier to get a team of decent Machamps (cloudy), Golems (partly cloudy) or Gyrados (rainy).
Weather Combat Effects
Attack moves of the boosted types are 20 % stronger. How the increased damage is calculated is not clear yet. Either the boost is applied to the base damage and rounded up before the normal damage calculation, as indicated in the affected Pokémon’s summary screens. Or the +20 % is just another factor in the damage formula, like STAB or type effectiveness. In any case, paying attention to the weather can make raid battles a lot easier.
Table 18: Weather conditions and boosted types (source)