To corroborate what others have already shared on this thread: Driving in cold weather does reduce the fuel efficiency very dramatically. This happens to all types of powertrains.
The graph below from Fuelly charts all my fuel-ups since May 2021 (this is a Sienna and not a RAV4, BTW, but the powertrains are very similar and their behavior in cold weather is similar).
You can see significant dips every winter, and the last and very cold (still on-going) winter has seen the mpgs drop to 30 vs. 40.5 long-term average. When driving in ideal driving conditions (65-75F = HVAC off, 45-55 mph, level terrain, good quality road surface, conservative driving style) you can expect the RAV4 Hybrid to push 45 mpg.
We just bought a 2025 Mazda cx50 hybrid which you probably know has the same RAV4 hybrid power train
The Mazda is a slightly heavier car but similar to the RAV4 the mileage people are getting seems to vary just as widely as with the RAV4s reported here
Ours is averaging 24-26 mpg (in mild climate and driving habits aimed at getting good mileage) which is 25-40% below the 39/37 rating for the car.
One of the biggest draws was the good results from real-world drive tests showing mileage in the high 30s to low 40s.
Given the tried and true history of this powertrain it seems like maybe the issues would have to do with computers or tuning. Toyota is king where hybrids are concerned and this one seems to be the rule
Anyway we are a week and a half into it and trying to sort out what the problem is. I will be filling up and resetting the mpg average and see what happens.
The CX-50 does have Toyota's hybrid system, but the engine, I believe, is Mazda's Skyactive rather than Toyota's A25A-FXS. The full-time Atkinson cycle A25A-FXS has the highest thermal efficiency of all gasoline engines; I imagine the part-time Atkinson cycle Skyactive is probably 20% less efficient from the get-go.