Here in IL, it has also been in the 60s lately, but not for the entire winter. Any decent stretch of days in which the temperature during your commute is below 40 degrees is enough to make a difference. I used to have a Buick that would get 30 miles per gallon all summer long, even with the a/c on the whole time, but as soon as winter set in, that went straight to 24 miles per gallon. My minivan typically goes from 20 mpg to 17 for the winter. Perhaps I’m too naive, but I have always chalked it up to a combination of winter blend fuels and the lower temperatures (ever notice how a winter breeze feels stronger than a summer breeze? Colder air is more dense, and your car has to push through that at 70 mph. That takes more fuel by itself)
Even if the mpg indicator is very accurate, it is indicating an average mpg. We have had unseasonably warm days here in the midwest. I filled up my gas tank on my Toyota Sienna at a station 10 miles from home. There was no traffic and only two stop signs back to my house. I drove about 45-50 mph and was not running the air conditioner as the outdoor temperature was about 50 degrees. My wife noticed that we averaged 26 mpg on this ten mile trip. This morning, we went to the grocery store which is 10 miles round trip. It was about 32 degrees and my mileage indicator now shows that I am averaging 21 miles per gallon. The first 10 miles after the fillup, I probably did average about 26 mpg. However, had I looked at the mileage for the 10 mile trip to the grocery store, I probably averaged about 16 mpg. Conditions make a lot of difference. When we make the 350 mile trip to visit my son and his family, I set the cruise control about 72 mph for the interstate. In cold weather, I will lose 2 mpg and if it is windy, I may lose another 2 mpg.
As long as an engine seems to be running smoothly and the transmission is shifting correctly, I don’t think your CRV has a problem.