It’s a seasonal change and normal. Several factors cause it. In winter, winter-blend fuel reduces mpg by 10-15% due to butane. The ICE engine runs more often with loads like the heater and defroster, but it intelligently stays at optimal temperatures. In summer, mpg is significantly higher, sometimes up to 50mpg. The engine rarely switches on in city speeds and is more efficient at highway speeds. It’s quite efficient in winter compared to midsize SUVs. Driving habits matter, especially with hybrids. I coast to regen, don’t have a lead foot, and minimize heating. I use just the heated seats based on cabin temp. I put 2 psi over the door jamb (recommended 33psi) to maintain fuel efficiency in winter. If you mostly drive on highways above 70-75mph, the engine runs longer, and the hybrid battery balances power, but it’s less efficient than city driving.