What does this symbol represent? Thanks
That symbol indicates the Pokemon is boosted by the weather.
There are various bonuses that take place when a Pokemon is boosted by the weather:
- When catching a Pokemon in the wild, their base IV threshold is 4/4/4, and you can catch them up to lv35 rather than lv30
- When catching the raid boss, the Pokemon will be lv25 rather than lv20
- Attacks that are affected by the weather receive a 20% damage boost