Pokémon GO has announced today that they’re experimenting with a special event called Legendary Lunch Hour where, on March 13, 2019 from 12:00pm to 1:00pm in your local time zone , there will be an increased amount of raids available for that hour.
Although this is currently only confirmed for March 13, it sounds as though if there’s enough participation and a positive enough reaction, it will be something they may offer as a weekly event.