Frames =/= lag. Frames are your computer's ability to render the game. It 'seems' like lag because you start to stutter but frames are a graphics processing thing not an internet/server connectivity thing which is what lag describes.
However, yes, both frames and server quality have been very bad with preseason. The servers have been having problems since mid-season earlier this year with a huge outage at the beginning of November. With patch 9.23 the changes in some of the map and especially with the new effects from the dragons some people are experiencing even worse frame rate problems because of badly rendering textures and over stress on older computer systems. One thing that helps is to go into your settings and lock your frame rate. I can usually get 160+ fps, but I lock it at 80 because it becomes more consistent across the game. It feels weird to be getting 160 then start entering a team fight and hit the 100-90's because of the added textures that are having to load with the champions and various VFX, so locking at 80 keeps it pretty much right at 80fps through the whole game.