While we are not from Ontario, but Manitoba, we have driven to Yuma many a time. Once you get to midwest you could possibly tie in to same route. We go as straight south as possible. We take I-29 south and then cut over to US81 and that ties into I-35. We then go cross country on Hwy 54 through NE and KS and tie into I-40 in Tucumcari, NM and west to Albuquerque. Once there we take I-25 south, and that is a beautiful drive for us, weather usually warms up in a hurry down that route, and we catch up with I-10 taking us through Tucson and then I-8 into Yuma. The odd time around Albuquerque we have come across some cool weather, sometimes snow, but have lost that pretty quick going down I-25. More concerning is your threat of snow/ice in the NE/KS areas. Just watch the weather forecast, download a good weather app, and keep your eye on forecast. If it's clear skies, the make hay, if bad weather in forecast, be prepared to hang tight somewhere and wait it out.
2016 Chevy Silverado 2500 Duramax
2016 Rockwood 8289WS, Diamond Pkg.