Large numbers of Orange-crowned Warblers winter in the U.S., from the lower Atlantic coastal plain states south through Florida and along the Gulf states through Texas. As warblers go, they do not range very far south, with the southern terminus of typical wintering grounds being northern Central America. So, an Orange-crowned Warbler attempting to ride out the cold season in Ohio doesn't seem like to much of a stretch.
But not so long ago, it apparently was. Excluding December records, which may represent very late migrants, Bruce Peterjohn in his scholarly work The Birds of Ohio lists only three verified January/February records of Orange-crowned Warblers. Bruce's revised edition appeared in 2001, so we're only talking two decades ago. A check of eBird records for January/February from 2001 to the present reveals about 20 records (and there are others). That's a huge increase in records. Either birders have become more adept at finding Orange-crowned Warblers or there are simply more of them to be found. I would lean towards the latter.
And it isn't just Orange-crowned Warblers attempting to ride out the snow and cold. This year's Columbus Christmas Bird Count documented three other warbler species in addition to one of the Orange-crowned Warblers, which was in the count circle. Yellow-rumped Warbler was predictable, as this is our hardiest warbler species and the only one that overwinters in numbers at this latitude. But Black-throated Green and Palm warblers (one of each) were decidedly unexpected. And possibly missed was Pine Warbler, one of which routinely overwinters at a local cemetery. However, the Pine Warbler is not a great surprise as it's our second hardiest warbler and probably routinely overwinters in Ohio, at least in forested southern regions.
While Orange-crowned Warblers have become nearly an annual wintertime phenomenon in Ohio, at least ten other species not mentioned above have been documented in January/February over the last decade. A number of them multiple times, too. They are Black-and-white Warbler, Black-throated Blue Warbler, Common Yellowthroat (another semi-hardy species and not completely unexpected), Magnolia Warbler, Nashville Warbler, Northern Waterthrush, Ovenbird, Tennessee Warbler, Wilson's Warbler, and Yellow-throated Warbler.
I'm sure other species will be added to the Ohio January/February list in coming years.