About a month ago DFW-LGA [for even mediocre weather LGA is prone to severe delays]. LGA had dense fog (I like window seats, so I can see landmarks), so severe that I couldn't the airport.* My flight (as well as all other DFW-LGAs) arrived 20 minutes early^.
Due to bad weather in ORD, ORD-LGAs were arriving 2+ hours late.
*Prior to landing, pax were required to turn ALL electronic devices off, so as not to interfere with the pilots navigation system.