Climate scientists sometimes talk about something called "climate departure" as a way of measuring when climate change has really changed things.
It's the moment when average temperatures, either in a specific location or worldwide, become so impacted by climate change that the old climate is left behind. It's a sort of tipping point. And a lot of cities are scheduled to hit one very soon.
A city hits "climate departure" when the average temperature of its coolest year from then on is projected to be warmer than the average temperature of its hottest year between 1960 and 2005.
For example, let's say the climate departure point for D.C. is 2047 (which it is). After 2047, even D.C.'s coldest year will still be hotter than any year from before 2005. Put another way, every single year after 2047 will be hotter than D.C.'s hottest year on record from 1860 to 2005. It's the moment when the old "normal" is really gone.