December/January southwest USA

Grand Canyon could be an option… warm down inside and no snow down inside… though possibly some at the top…

More than likely to have snow on the rim of the Grand Canyon. North Rim will be closed. South Rim will have snow and steep trails with lots of exposure. If this makes you nervous, hike somewhere else.

Death Valley might suffice in most areas except the higher peaks. In the book Salt to Summit: A Vagabond Journey from Death Valley to Mount Whitney by Daniel Arnold he hikes cross country so if you are into off trail there are so many places you can go and go and go. Read it and see if you can get some insight. You may want to avoid Whitney with your aversion to an inch of snow. lol However Death Valley being the biggest National Park in the lower 48 should afford all the hiking you need. It is immense. We did have some snow flurries in one of the higher passes there in one of the shoulder seasons but down low you should be fine. Near the southerly areas the Death Valley Germans were lost and finally found so again the scales of that place are immense. There are several areas of amazing sand dunes that are fun. We hiked them a lot. That’s even fun at night and the time of year you desire will have some long nights. Well, just a thought. There is a lot public land in the southwest to consider but lots are off the radar and remote.

Joshua Tree southern entrance of of I-10. Whitewater and Mission Creek Preserve. Long Canyon out of Desert Hot Springs. The snow can get down to 3,000’ a few times a year. The higher elevations of JT, may or may not get snow. They still may be cold.  Anything south of Phoenix and west of Tucson should be fair weather. The area between Gila Bend and Tucson can be really nice. Depends what you want to see.