The question of when fall begins is not simple, especially for residents of the Deep South. There is a fundamental difference between the formal dates used by scientists and the actual experience of the season. The transition from summer to autumn is marked by two distinct measurements: one tied to the solar system and the other to fixed calendar months. Understanding both definitions helps explain why Mississippi often seems to celebrate fall before the weather actually cooperates.
The Astronomical Start Date
The traditional start of the season is determined by celestial mechanics, specifically the Autumnal Equinox. This moment occurs when the Sun crosses the celestial equator, an imaginary extension of Earth’s equator into space. Astronomically, this is the point in Earth’s orbit when neither the Northern nor Southern Hemisphere is tilted toward the sun, resulting in an almost equal duration of daylight and darkness across the globe. The date of the equinox is not fixed, typically falling on September 22nd or 23rd in the Northern Hemisphere. This slight annual variation happens because the Earth’s orbit around the sun is approximately 365.25 days long, requiring the calendar to adjust with a leap year every four years. Following this definition, fall lasts until the Winter Solstice in December, marking the shortest day of the year.
The Meteorological Definition
Meteorologists and climate scientists use a different, more consistent system to define the seasons. This definition divides the year into four three-month periods based on the annual temperature cycle, aligning perfectly with the Gregorian calendar. Under this system, fall officially begins on September 1st and concludes on November 30th. This fixed calendar approach ensures that seasonal data is easily comparable across different years and locations. By grouping three full months together, scientists can maintain consistent records for climate tracking and forecasting, which avoids the shifting dates of the astronomical equinox. This standardized method allows for a uniform division of the year, making it simpler to calculate and analyze seasonal temperature and precipitation averages.
The Practical Reality of Fall in Mississippi
For people in Mississippi, the official start dates often feel theoretical, as the practical reality of fall lags significantly behind the calendar. Hot and humid weather frequently persists well into September and October. Consistent, cooler air masses that signal autumn generally do not settle in until late October or early November.
The average date for the first frost across the state is a good indicator of sustained cool weather, demonstrating this delay. Northern parts of Mississippi may see their first frost around late October, but the dates shift later toward the Gulf Coast. Along the southern coast, the first frost often occurs in late November or early December. This range shows how prolonged the summer weather can be, especially in the southern half of the state.
Foliage change, another hallmark of fall, happens much later in Mississippi than in many other parts of the country. Peak color is triggered by shorter daylight hours and consistently cooler temperatures, both of which arrive slowly. Trees, including sweetgums, maples, and oaks, typically begin their vibrant display in late October.
The most brilliant colors are generally not seen until November, with the timing varying by region. Northern Mississippi tends to reach peak foliage around the beginning of November, while central portions peak around mid-November. Coastal counties can experience their peak color as late as the third or fourth week of November. This makes Mississippi one of the last states to display its full autumn palette, meaning the experience of a true Mississippi fall is often a phenomenon of November.