With Labor Day weekend fast approaching, we know the fall season will soon be upon us. In fact, “Meteorological Autumn” begins Sept. 1– four days before Labor Day. Meteorological Autumn continues through the end of November. This three month period differs from “astronomical autumn,” which begins on September 22nd and runs to December 21st.
The meteorological seasons, while they don’t exactly coincide with the astronomical seasons which are defined by the position of the sun overhead, do include changes in weather reflective of the season.
It's snowing in Colorado! Portions of the Rocky Mountains woke to the white stuff Wednesday morning. WeatherNationTV.com – Video: Loveland Ski Area
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Toward the start of summer, the northern hemisphere observes less daylight each day through the end of fall. The result– much cooler temperatures across the U.S. and a change in weather patterns. At higher latitudes, especially at the poles, daylight hours shorten faster where cooler temperatures set in first. Transport of cooler air from higher latitudes into the lower 48 will often times collide with much warmer, moist air still in place. This latitudinal activity is similar to what we see during the spring season and can bring severe weather and tornadoes. It is widely accepted that through the fall, especially through October and November we see an uptick in the number of severe thunderstorms. This is considered a second severe weather season to the spring severe season in the U.S.
Late Summer into Fall the cooler air transported south will also give us more opportunity for snow especially at higher elevations. Across some of the highest mountain peaks in the US snow can occur any time of year but certainly becomes more common as we head through fall and into winter.
For WeatherNation: Meteorologist, Mike Morrison