The sun is the grand agent in diffusing heat over the earth’s surface.
While the sun is above the horizon of any place, that place is receiving
heat; and when the sun is below the horizon, it is parting with it by
the process called “radiation.” Whenever therefore the sun remains more
than twelve hours out of the twenty-four above the horizon of any place,
and consequently less than twelve hours below, the general temperature
of that place will be above average; and when the reverse occurs, it
will be below average. If the temperature depended solely on the heat of
the sun, then indeed a tolerably accurate view of the respective
climates of the zones of the globe might easily be assumed; but it is so
greatly modified by other circumstances, that considerable differences
prevail in countries situated in the same parallels of latitude.