September 21, 2018 was the official first day of astronomical fall. For meteorologists around the country, meteorological fall began on September 1st. Why is there a difference between the astronomical fall date and meteorological date? It’s actually more than just the fall start date. Each season’s start and end is different for both. For astronomy, the basis of the seasons is the natural rotation of the Earth around the sun. This sets up the astronomical calendar for which there are two solstices (summer and winter) and two equinoxes (vernal and autumnal). Each of these corresponds to the changing of the seasons for the astronomical calendar. For meteorology, a grouping system of three months based on the annual temperature cycle. Winter, we usually think as the coldest with summer being the hottest. Spring and fall are transition seasons for which the temperatures tend to shift to the next extreme.
Now that the differing seasonal dates have been explained, let’s talk about the recent trend in increasing temperatures for fall. Out of 244 cities analyzed, roughly 80 percent have warmed at least one degree Fahrenheit in the last half-century. This is compared to the one percent which have cooled one degree Fahrenheit or more. The last three fall seasons have been within the 10 warmest on record. With this increase in temperature, the beginning parts of fall have felt like an extension of summer, with the last characteristically hot day in most states coming later and later in the year.
Warmer falls will undoubtedly delay the peak fall foliage and cause leaves to drop more quickly, shortening the leave color change season. Also, insects will tend to linger around for a longer amount of time because the first freeze of the year will come later in the season. These are just two of the many impacts that a warmer fall can have on the United States. Make sure to check the link below to see the warming trend in your city.
To see what trend your nearest city has, check this link to find out.
To learn more about other interesting stories related to global climate issues, be sure to click on the following link: www.globalweatherclimatecenter.com/climate
©2018 Weather Forecaster Alec Kownacki