It gets its name because the front moves south and west, rather than north and east like fronts usually move. This type of front usually stalls on the eastern Appalachian mountains, keeping mild air over our region. But this particular back-door front will keep moving and reach Delaware by Saturday. That puts most of our region under some chilly air from New England. Tuesday we told you how the days are getting longer.
Daylight lasts over an hour and half more now than it did on the first day of winter.
They're in this AccuFacts file. The first reason is the earth's tilt. Our planet's axis stays tilted 23-degrees from vertical all of the time. The angle between the sun and the earth's axis means the northern and southern hemispheres get different amounts of sunlight. The second reason is the earth's orbit.