The release of 50 Gen 3 species on 12/8/17 coincided with the debut of another major (and probably more impactful) mechanic: weather. Through this feature, Niantic not only pays homage to weather effects from the main series games, but also incorporates another aspect of the real world into its hit AR game.
Each type of weather is tied to 2 or 3 Pokemon types. Weather has 3 main effects in the game:
- Pokemon of a weather’s corresponding types spawn at increased rates
- Wild Pokemon of a weather’s corresponding types yield extra Stardust and have higher level and IVs when caught
- In battle, moves of a weather’s corresponding types get a power boost
Pokemon GO appears to use forecasts by AccuWeather, which reports weather data obtained from various services, such as the National Weather Service in the United States. Pokemon GO assigns weather to geographic areas (“cells”) based on the hourly weather forecast provided by AccuWeather (emphasis on forecast: GO does not use the current weather). The active weather in-game is updated every hour, on the hour.
Due to the size of individual map cells and the innate inaccuracy of weather forecasts, don’t be surprised if the game’s active weather does not reflect real-world weather!
Pokemon GO also defines extreme weather based on weather warnings - any sort of warning - reported by AccuWeather. This can lead to the game having extreme weather despite completely benign warnings such as “unseasonable mildness” or “extreme surf.”
In the overworld, active weather boosts spawn rate for Pokemon of that weather’s corresponding types. Such Pokemon have a swirling wind animation.
Ex: In cloudy weather, Pokemon such as Marill, Jigglypuff, Ralts, Machop, Mankey, Makuhita, Weedle, Gastly, and Gulpin get increased spawn rates.
Very little research has been conducted to quantify to what degree weather affects spawns. Based off preliminary scanner data, the effect is substantial. Anecdotally, weather does not affect all species equally. It appears that Pokemon who rarely naturally spawn in a biome barely benefit from active weather.
Ex: In locales where Torchic is very rare, Torchic will remain very rare even when sunny/clear weather is active.
Wild Pokemon that are influenced by active weather (i.e., have the swirling wind animation) are affected in 3 ways during a catch encounter:
- When caught, they yield +25% extra Stardust
- Their IV range is 4-15 for each stat rather than the usual 0-15
- They are 5 levels higher than normal, in a level 6-35 range
The latter 2 effects have not been extensively researched, but there is a wealth of evidence that argues for them. Note that players between level 30-34 are still able to encounter wild Pokemon of level 35, suggesting that the 5 levels are “added” to the encounter.
Pokemon that spawned due to one type of active weather may no longer benefit when the weather changes. Their IV and level range revert to the range for normal spawns.
Raid bosses do not get any modifications to their IV range, but they are encountered at 5 levels higher than normal, i.e. level 25.
In battle, active weather boosts power for attacks of that weather’s corresponding types. Niantic is transparent about this mechanic and displays these boosts on a Pokemon’s info page.
Ex: In cloudy weather, moves such as Dazzling Gleam, Counter, Dynamic Punch, Poison Jab, and Sludge Bomb get increased power.
Boosted moves get a 1.2x power multiplier. Note that fast move bonuses displayed by the game are not always accurate if the fast move’s power is indivisible by 5. In these cases, the displayed boost is rounded to the nearest integer, but the boost used in damage calculations is not rounded.