2019 had a cold SW, warm NW pattern in May but then California warmed up by early June. What's amazing is both May 2019 and May 2023 have now averaged below 70 F in Downtown LA, which does not happen very often. It only happened about 25 times since records began in 1877.
2020 had a very weak monsoon but I'm not sure if that was because of a weak 4CH or the 4CH being too strong and too far north.
It seems climate change is causing patterns of persistent troughing next to persistent ridging and more blocking patterns.