I´ve never had this problem before. I´m having huge FPS drops since the game updated into patch 9.22, when I say huge is because it is actually HUGE! about 50-60 FPS drop every 10 seconds! I literally can´t play League at least on SR. The most interesting part is that I can play on other maps fluently.
I formatted the PC but I´m still having the same issue.
My PC isn´t the best PC in the world, but in the last 4 years I´ve never had a problem with it so I concluded that this must be an issue that is coming from the game itself and not from my PC.
Edit: I´ve sent FOUR tickets to Riot´s support and they sent me the exact same answer in ALL of them: "It´s a problem from your PC" man I´m sorry for the language but this is getting DISGUSTING! The support is copy pasting the exact same text for those who have been experiencing this issue, my gosh how can a company just ignore such a large amount of players having this issue! This is an in-game otimization bug that has been happening for months already and it´s getting worse and worse!