I get 30 city to 38hwy on my 2021 non hybrid, try another dealer. Are you filling it then driving 100 miles then refilling at the same pump to see actual miles?
There are any number of factors that can affect mileage. What state are you in, Have you checked tire pressures, Are you driving in the snow, Stop and go traffic should actually give you better mileage because of the hybrid feature. Outside temperature and how long is the trip.
Try filling with Chevron gasoline and then going back to the same pump after a hundred miles

 

FWIW:


Cold weather and winter driving conditions can significantly reduce fuel economy. Fuel economy tests show that, in city driving, a conventional gasoline car's gas mileage is roughly 15% lower at 20°F than it would be at 77°F. It can drop as much as 24% for short (3- to 4-mile) trips.

 

On a short drive, especially in very cold weather. The fuel mix for the engine stays richer to keep it running smoothly. That is a given, but my RAV4 for it's still gives me 30 m p g for an 8 mile run at 50 degrees

 

All vehicles take a hit to MPG during the winter.

Mainly, your car uses more energy (gas/electricity) to keep the engine and battery at operating temperature and keep the cabin warm for passengers.

Your MPG will go back up when the weather warms up.

 

There's also the increase in ethanol for a lot of States during the winter months. This will tend to lower fuel mileage also.

 

My beloved RAV gave me 39 mpg when I first bought it last summer, but by now (January), it's at 33.2 mpg. I took it to the service garage at our local Toyota dealership and they told me nothing was wrong--this was normal.

IS IT???

How many miles on the vehicle?
Where do you get your gas? What kind do you use?
Where do you live?
What have the temperatures been like? Low increases wind resistance the car pushes through, you use more HVAC so ICE runs more often.
Any extended periods of rain or snow? Increased tire resistance.
Much driving in them?
Checked your tire pressures recently? Lower than 35?
Checked your oil level recently? Overfill is bad.
Any changes due to driving distances, types of trips, frequency of trips?

 

My beloved RAV gave me 39 mpg when I first bought it last summer, but by now (January), it's at 33.2 mpg. I took it to the service garage at our local Toyota dealership and they told me nothing was wrong--this was normal.

IS IT???

You got 39 mpg driving a house down the road. You should be happy ;-)

As many others have pointed out already, colder weather + lower energy density winter gas + lower tire pressure can do it.

 

YES!

Summer = WARMER ambient temps = 39mpg
Winter = LOWER ambient temps = WORSE mpg
1,000,000% NORMAL.

Why? Car is burning more gas to maintain operating temps. Just like your Winter gas/oil usage increases b/c you are using the heater more to maintain warmth.

Don't forget to check the tire pressure. Every 10F drop=1psi drop.

Consider just driving during the warmer months (Spring/Summer) to maintain higher MPG.

 

Consider just driving during the warmer months (Spring/Summer) to maintain higher MPG.

Precisely

And your other option is to let this house go, and get a real car (Hint: Camry has the same powertrain as this one)