As circumstances change, what we think of as normal and healthy -- the baseline -- shifts to keep up with experienced reality.
The new normal tends to surface after two main sorts of occasions: traumatic national events — like the World Wars and 9/11 — and catastrophic economic events: the Great Depression, the oil embargoes of the 1970s and the market crash of 2008. The phrase began to be associated with global warming around the early 2000s and its use has ramped up in reference to extreme weather events driven by climate change; also after disastrous wildfires, hurricanes, heatwaves and drought. All of these circumstances have something in common: they are times of transition and times of uncertainty; they describe situations that are radically different than what came before them.