What actually happens in the cold
Three compounding effects: cabin heating draws kilowatts (resistive heat especially), the battery chemically resists charging and delivering, and winter tires plus slush add rolling resistance. Net effect at freezing: 20–30% less range; at 0°F with hard HVAC use: up to 40%.
Planning with the seasons
Build two range assumptions into your mental model: the EPA figure for mild weather and about 75% of it for winter highway driving. The road-trip planner here takes a buffer input for exactly this — set it tighter in January.
Small habits that recover most of it
Precondition while still plugged in (cabin and battery warm-up on wall power is nearly free), use seat heaters before cabin heat, park plugged in overnight in deep cold. None of these fixes chemistry; together they get winter losses down to a shrug.