No matter whether you go by the astronomical calendar or the meteorological calendar, both agree that the country has now entered fall.
The autumnal equinox officially occurred on Monday at 2:19 p.m., when Earth’s alignment allowed the Sun to be directly over the equator. This marks the point of the year when there are roughly equal amounts of daylight and darkness.
For the Northern Hemisphere, however, daylight hours are now on a steady decline as the region heads toward winter.
In addition to the shrinking daylight, temperatures also see their biggest drops of the year.
For instance, along the Interstate 20 corridor in the northern part of the state, average highs usually reach the mid-80s in late September but plummet to the 50s during the final weeks of astronomical fall.
Further south along the Interstate 95 corridor, daily highs typically start in the low to mid 80s at the beginning of the season before sliding to around 60 degrees by its end.
It is also the time of year when the first frost and freeze typically occur but in recent decades, the first dates have been arriving later than normal.
In the Upstate the first frost usually occurs in early to mid-October, with the first freeze in later in the month into early November.
The first frost and freeze dates can vary significantly along the coast, where a warm Atlantic Ocean helps to moderate the terrain, delaying the onslaught of cooler weather by at least a month.
Meteorologists and climatologists officially define autumn as the full months of September, October and November.
According to NOAA, using these three-month blocks for each season makes it easier to compare records and analyze long-term climate data, rather than adjusting dates each year based on the astronomical calendar.
Whichever calendar system you follow, Mother Nature’s version of fall will feel anything but autumn-like in the days ahead.
Back to summer-like regime
For most of the state, the start of astronomical fall will be met with temperatures running 5 to 15 degrees above average.
An easterly to southerly flow is allowing temperatures to feel more summer-like, with temperatures into the 80s and 90s.
There are generally two ways that kind of heat can break - either a cold front or a tropical system. Neither of which are expected to impact the state over the next few days, meaning the warm pattern will linger for a while.
Wednesday and Thursday appear to height of the fall heat wave, before a cold front arrives for the weekend.
The combination of warm, dry weather may have complications for many trees that will start showing their changing leaves.
Fall foliage outlook
Anderson has recorded a shortfall of nearly 5 inches of rain for the year, while Aiken and Florence are closer to 7 inches below normal, which can impact the internal processes within plants.
This year’s peak activity is expected to roughly fall from October 13 through the first few days of November.
