Since cars have integrated phone-home diagnostic software, why would the government even allow automakers to advertise 'estimated' ranges for specific car models and not simply show actual averages?
My point is that it isn't as simple as an average due to the massive temperature sensitivity. It applies to ICE cars too, but it certainly isn't as noticeable as the engine allows a wider range of temperatures. Ironically the EV is proposed as something to battle climate change, but it is much more susceptible to it's effects.
https://www.fueleconomy.gov/feg/hotweather.shtml
Personally my ICE goes from ~22-23mpg to ~19 when it's like 100F outside. That's a 17% drop in mileage. My EV has had a bit of a hit but not nearly as much, <10%. I can even offset that a bit more by ensuring I plug in and precondition before I leave, meanwhile my ICE will always burn it's gas to cool down even if I had remote start.
Heating is usually "free" energy-wise though since the gas motor is just leaking massive amounts of heat all the time.
It ought to quickly adapt to weather pattern changes quickly enough while not being too "jumpy".
My ICE car can display MPG and distance to empty it seems to do something like that instead of displaying some random preconfigured metric.