Tropical weather systems, like the one developing along and off the Southeast U.S. coast, derive moisture and critical latent heat energy from the warm ocean waters—like those we see in these ocean analyses out of CIMSS at the University of Wisconsin-Madison

Both of these graphics and analyses are courtesy of CIMSS (the Cooperative Institute for Meteorological Satellite Studies) at the University of Wisconsin-Madison:

Seasons on Earth ARE DUE TO EARTH’S ORBIT OF THE SUN and the tilt of Earth on its axis relative to the Sun

This ORBIT AND AXIS TILT results in a shift in the amount of sunlight which falls on Earth at different times of the year.

As we approach winter, the sun’s most direct sunlight falls farther and farther south of the planet. We watch here in Chicago as the sun’s trek across the sky each days shifts farther south gradually each day. The more southerly the track of the sun across the sky each day means we see the sun for shorter periods each day. This is why it is that days grow shorter. It also means the sunlight which arrives here at ground level each day heading toward winter does so at an increased angle. As this happens, we receive less energy from the sun each day. Shorter days and less energetic sunlight is why temps cool through autumn moving toward the onset of winter. The winds around weather systems can blow warmer air into the area leading to “ups and downs” in the rate of cooling—but the OVERALL AUTUMN TEMP TREND is lowers.

Historically, normal temps pull back 10 degrees in September, 12 degrees in October and 13 degrees in November—making them the first, second and third-fastest cooling months of the year here in Chicago.