Besides the fact that "North" implies "cold," and "South implies "hot," I was struck by the fact that Lincoln won absolute majorities (in a four way race) in 16 states wholly or partially above the 41st parallel (the coldest states), while winning only one "hot" state (California), south of that line.
Although they were "slave" states south of the Mason-Dixon line, the border states of Maryland, Delaware, Kentucky, and Missouri are "cold" states (to be defined shortly). And they all went for the Union.
Also "cold" were one state, West Virginia, that broke away from the Confederacy, and one wannabe "East Tennessee." Although they are in Southern latitudes, their location in the Appalachians makes them "cold."
For the purposes of the question, "cold" means "colder than Richmond Virginia" (basically the coldest part of the Confederacy) in January (as a litmus test). That would be an average of about 40 degrees Fahrenheit.
A "region" is at least one third or so of any one of the 33 states of the United States on November 6, 1860 (Lincoln's election). A state may be divided East, Middle, and West on an east-west axis or north, middle and south on a north-south axis. E.g. East Tennesseee, West Virginia, North Alabama.
California, a "hot region" (whole state, actually) was exceptional in being pro Union, rather than pro Confederacy.
Apart from California were there any "hot regions" that were pro Union and had little or no interest in slavery? Conversely, were there any "cold regions" that were strongly pro Confederacy/slavery? Is there something I have overlooked in constructing this hypothesis?