When I had my Ford Escape, I counted on getting lower MPG due to a number of factors, mostly the increased rolling resistance caused by snow on the road, lower tire pressures due to lower air temperatures, higher drag due to increased air density and frozen precipitation on the car's body, and increased electrical power required by lighting and accessories like wipers. Since ICE are not as efficient as an EV, the energy they normally waste means these impacts are not as significant as when you drive an EV.
The Volvo PHEV I drive now will drop to its EPA range in the Winter (35 Miles Electric range) while I am seeing 50 miles of EV range in the summertime. I don't have a heat pump, but a resistive heater which uses a Watt of electricity to produce one watt of heat energy. It's better to heat the seats and steering wheel (still resistive, but targeting the contact points with less power). ICE is so bad at converting gasoline into forward motion that all that heat can be used to heat up the cabin. That's great when it's cold, but wasted when it's hot out.
Same thing with braking, ICE just heats up the air by rubbing friction material against steel disks (or drums). EV captures the kinetic energy and puts most of it back into the battery.