That explains a lot, I have the same issue. Occassoinally ill just rubber band around and my ping will go from 80 to "200ms" but really, the on screen effects are more around 2 solid seconds.
This is mostly caused due to packet loss, basically bits of information being sent to riot or to you being lost in ATTs mass bandwith.
Riot has contracts with many providers to have certain access tunnels for the info of their players so you dont have to worry about being lost in verizons mass of users.
ATT and Riot do NOT have this contract, and sadly packet loss might be un avoidable.
THings to do before starting a game is to reset your pc, and your router. Give your WIFI card a fresh start and stuff and ust hope you arent gonna lag next game.