Niantic has reduced the rate at which Raid Bosses release charged attacks in Pokémon GO in response to increased difficulty of Raid Battles

Niantic has provided the following update aimed at Pokémon GO players:

Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change. Be sure to follow Niantic on social media, opt in to receiving push notifications, and subscribe to Niantic’s emails to stay updated.

Source: Official Pokémon GO support

Source:Pokémon