Pokémon Go Tips: How Pokémon Spawns and What Affects the Spawn
So it comes to how Pokémon spawns and what factors affect the spawn. A group of players has done a field test and research on the mechanism and come out with some theories based on the data they gather. We summarize the study with points.
Note: all these are theories and they are for your reference only.
Ground, Rock, Fire, and Fighting type Pokémon have significant correlations with temperature, humidity, cloud cover, clear weather and wind.
It's very likely (the team says they are 95% sure about it) that Water type Pokémon have significant correlations with riverbanks (most strongly correlated), wetlands, saltwater beaches, canals, docks, and parks with water features like ponds. However, lakes, streams and dams seem to have weaker correlation with the spawn. You can see all data in the table below.
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3. What Pokémon spawn in desert or dry area more often?
4. What Pokémon spawn in forest or grassland more often?
5. What Pokémon spawn in coastal areas more often?
6. Rain or thunder storm seem to have no influence on Pokémon spawn.
7. Ghost type Pokémon doesn't seem to spawn in cemeteries more often than in other places.
Source: The Silph Road