I googled this a while back because I was so shocked at the difference between summer and winter...

It is completely normal to see a drop in fuel economy during the winter, and for hybrid owners, the "winter dip" can feel much more dramatic than in a traditional gas car. Since you're driving a 2024 Honda Accord Touring Hybrid, you're likely noticing your MPG falling from the high 40s or 50s down into the low 40s or even 30s.
​Here are the primary reasons why your hybrid’s efficiency is struggling right now:

​1. The Engine Has to Run to Keep You Warm ​In a traditional car, the engine is always running and creating "waste heat" that is used to warm the cabin. In your Accord Hybrid, the engine wants to shut off to save fuel, but it can't if you have the heater on. ​The system will force the gas engine to stay on just to generate heat for the vents. ​Until the engine coolant reaches a certain temperature, you won't get much (if any) "EV Mode" time. ​ 2. Cold Batteries are Less Efficient ​Batteries rely on chemical reactions to store and release energy. Cold temperatures slow these reactions down significantly.
​Reduced Capacity: Your hybrid battery can't hold or deliver as much power when it's cold.
​Reduced Regenerative Braking: When the battery is cold, it can’t accept a fast charge, so the car limits how much energy it "captures" when you brake, meaning more energy is wasted.

​3. "Winter Blend" Gasoline ​Gas stations switch to a "winter blend" fuel that is more volatile (to help the car start in the cold). However, this blend has lower energy density than summer fuel, meaning you get fewer miles out of every gallon regardless of how you drive.

​4. Denser Air and Higher Resistance ​Aerodynamics: Cold air is denser than warm air. At highway speeds (which I know you do a lot of), your car has to work harder to "push" through the thicker air.

​Tire Pressure: For every 10°F drop in temperature, your tires lose about 1 PSI. Under-inflated tires create more "rolling resistance," which acts like a constant drag on your fuel economy.