From the physics, it seems range calculations with electric cars should more accurate
Looking at the physics, a battery powered car should not be affected by wind or rain any more than any other kind of car -- wind and rain reduce milege through their effect on wind drag and rolling resistance, which does not vary with the engine.
An electric car should be less affected by stop-and-go traffic than a combustion engine car which needs to keep running while stopped. Mind you, in adverse weather any kind of car still needs to expend energy heating or cooling the interior when stopped.
The joules consumed to heat the interior will not vary according to engine type, but in a combustion engine waste heat can be used. When waste heat is put to a useful purpose, overall efficiency goes up.
And electric motors very efficient and the types you would use in a car are very efficient over a wide range of rotational speeds.
Electric motors are often over 90% efficient. The inefficiency comes in generating, transmitting and storing the electricity.
Electric cars will have their range vary with *temperature* a lot more than cars with fossil fuel or fuel cell engines. That is the only respect in which their range should be less predictable than other cars.
But then it ought to be possible to obtain a temperature forecast for the next 8 hours and accurately predict range from that. (I imagine that if the US's National Weather Service does not broadcast a machine decodable temperature forecast it will in the foreseeable future. Until then manual entry would be required, as is done in aircraft.)