Meteorological Fall Begins Tuesday — So Why Is It Going to Be 96 Degrees?

September 1 marks a date many weather lovers have been waiting for: the beginning of meteorological fall.

There is just one problem.

Someone apparently forgot to tell the atmosphere.

Instead of crisp mornings, comfortable afternoons and sweater weather, the first few days of September will bring some of the hottest temperatures we've seen recently across Rowan County and the surrounding region.

High temperatures are expected to climb into the mid and upper 90s during the middle of the week, with humidity making it feel even hotter.

So how can it be fall when it still feels very much like the middle of summer?

The answer comes down to what meteorologists actually mean when we say "fall."

Meteorological Fall Begins September 1

There are actually two different ways of defining the seasons: meteorological seasons and astronomical seasons.

Meteorologists and climatologists divide the year into four three-month seasons based largely on the annual temperature cycle and the calendar.

In the Northern Hemisphere:

• Meteorological spring is March through May.
• Meteorological summer is June through August.
• Meteorological fall is September through November.
• Meteorological winter is December through February.

That means meteorological summer officially ends Monday, August 31, and meteorological fall begins Tuesday, September 1.

Using complete calendar months makes it much easier for meteorologists and climatologists to compare temperatures, rainfall and other weather statistics from one season to another.

Astronomical fall is different. It is based on Earth's position relative to the sun and begins around the autumnal equinox later in September.

But neither definition of fall means that Mother Nature has to immediately turn down the thermostat.

September Can Still Be Very Hot in North Carolina

One of the biggest misconceptions about meteorological fall is that September 1 should immediately bring cooler weather.

It doesn't work that way.

The transition from summer into fall is gradual, especially here in North Carolina.

The days are becoming shorter and the sun angle is gradually decreasing, but there is still plenty of energy available to produce hot afternoons during early September.

Large-scale weather patterns also matter much more on any individual day than the date on the calendar.

And this week we have a weather pattern that strongly favors heat.

A Strong Ridge Is Taking Control

A strong area of high pressure in the upper atmosphere is expanding eastward toward the Carolinas.

Underneath this ridge, sinking air makes it difficult for clouds, showers and thunderstorms to develop.

That means we get plenty of sunshine.

It also allows temperatures to climb.

Across Rowan County, the forecast calls for a high near 94 degrees Tuesday before climbing to around 96 Wednesday and Thursday.

Cabarrus County could be even hotter, reaching around 95 Tuesday and 97 Wednesday and Thursday.

Davie County is forecast to reach the mid-90s, while Davidson County should climb from the lower 90s Tuesday into the mid-90s by Thursday.

Those temperatures would feel much more appropriate for July than the beginning of meteorological fall.

The Humidity Makes It Even More Noticeable

Actual air temperature is only part of this week's story.

Humidity will remain elevated, with dewpoints expected to stay around the lower 70s at times.

When temperatures in the mid to upper 90s combine with that kind of moisture, the heat index can climb above the actual temperature.

Rowan County could experience a heat index around 100 degrees Tuesday.

In Cabarrus County, the heat index could reach around 102 Tuesday, with potentially higher values possible as the heat peaks during the middle of the week.

The broader weather pattern supports the possibility of heat index values reaching the low 100s during the hottest afternoons.

That means our first few days of meteorological fall won't just be hot.

They could feature potentially dangerous heat.

Fall Is a Transition, Not a Switch

This week's forecast is actually a good example of why we shouldn't think of seasons as switches that suddenly flip on a particular date.

September is a transition month.

We can still experience summer heat, humidity and thunderstorms, while gradually beginning to see signs that autumn is getting closer.

Daylight continues decreasing.

Average temperatures gradually decline.

Cold fronts eventually become stronger and more frequent.

Humidity begins trending downward.

And over the coming weeks, those changes become increasingly noticeable.

But the atmosphere doesn't care that the calendar says September 1.

If the weather pattern supports temperatures in the upper 90s, that's exactly what we'll get.

There May Be a Hint of Change by the Weekend

Interestingly, while meteorological fall begins with a blast of summer heat, we may get a small reminder of the changing season by Labor Day weekend.

The ridge responsible for this week's heat is expected to begin weakening late in the week.

A disturbance and cold front could approach the Carolinas Friday, bringing our next meaningful chance for showers and thunderstorms.

Behind that front, there are indications that somewhat drier air could move into the region.

That doesn't necessarily mean dramatically cooler temperatures immediately, but lower dewpoints could make the air feel considerably more comfortable.

There are also indications that portions of the region could see temperatures return to the 80s during Labor Day weekend if the front progresses as currently expected.

That's something I'll be watching closely over the next several days.

And Yes, Fall Foliage Season Is Coming

There's another reason September 1 is an important date this year at Rowan County Weather.

Tuesday will also bring my first Fall Foliage Forecast of the season.

Don't expect widespread fall color across our region yet. We're still at the very beginning of the transition.

But over the coming weeks, I'll be tracking how temperatures, rainfall, elevation and changing daylight conditions influence the progression of fall color across North Carolina and the surrounding region.

We'll gradually watch those autumn colors work their way from the higher elevations into the foothills and eventually toward the Piedmont.

For now, however, you'll probably want to keep the shorts and sunscreen handy.

The Bottom Line

Meteorological fall begins September 1 because meteorologists define fall as the months of September, October and November.

It does not mean cool weather automatically begins September 1.

This year is going to demonstrate that point very clearly.

Rowan County could reach 94 degrees Tuesday and around 96 Wednesday and Thursday, while some nearby locations could approach 97 degrees. Combined with high humidity, heat index values could reach the low 100s.

So yes, Tuesday is the first day of meteorological fall.

And yes, it could feel like the middle of July.

Welcome to September in North Carolina.