Eastern Ontario, Canada, to Arizona in January

I was about to write a lot before I read Jaxdad.

He hit it square.

As I hope you will cross at Thousand Islands and not go farther west, running southwest about 100 miles in from the coast is a good idea. Target through Harrisburg PA. By Nashville you should be 90% clear. You will have to watch the weather on your own.

We used to travel in cold weather all the time. As said, this is where a MH has an advantage, but there is no reason you can't try to travel with the gas and heat on. If I were to do that in your case, I would get a remote thermometer so I could know the temperature in the back.

Matt

Having done the sprint south to warmer temps more times than I care to think about, albeit having a few hours head start on you, I'd suggest a slightly different theory.

As mentioned, I have the advantage of having a motorhome which means I can easily keep the living quarters warm as I drive. I have a warm place to spend the first night.

The most important suggestion I can give you is to be flexible in your departure and keep a close eye on the weather, there's no use driving in bad weather if you can avoid it. Along with that idea I would recommend you take the 401 east to Sarnia then on to Indianapolis and Nashville. The south side of Lake Erie is notorious for lake effect streamers and white outs, even on 'sunny days'. It also means you won't be driving on anything but pretty flat land.

Depending how hearty you are, you might want to consider spending the first night in a hotel / motel instead of sleeping in a cold trailer.

Why are you worried about dewinterizing? Just carry some jugs of water. 5-6 gallons should be plenty. You can always refill them at FlyingJ for free.
I would head for Nashville, TN then to I55 at Memphis and if the weather permits dewinterize at the FlyingJ north of Nashville.
If you cannot dewinterize at the Nashville FlyingJ then head toward Memphis and dewinterize at the FlyingJ there.
Before you dewinterize you can still use the toilet and If you need a shower buy one at FlyingJ/Pilot. Two of you can fit in the shower area nicely. Refill water as needed
My route would be I81 to Bnghamton and then I86 to I90. I90 to I271/71 t Louisville and then I65 to Nashville.
You could actually spend a day or 2 at a Nashville CG and dewinterize and see the Grand
Ol Opry or a lot of other things
January through Pennsylvania, Virginia do not thrill me at all. Add the mountains. I would not be happy

If it were me I'd have several routes worked out, and take the one forecasted to be warmest.

My default choice would be to get directly south as quick as possible: I-81. By the time you get in Virginia the odds are in your favor.
Next bet would be to head for the midwest and take the Mississippi River route south.

Short answer: yes.