September is a time in which summer ends and autumn takes hold. This year’s September seemed to reverse that order of events. (Made Nagi/EPA-EFE)

September, which ended at midnight on Saturday, seemed to provide Washington with two months in one, welding together two periods with decidedly different weather personalities: a cool, fairly damp first half and a warm, sunny, no- rain- at- all second half.

Often regarded as a kind of swing month, September is usually the time of year in which steamy summer gradually gives way to encroaching autumn.

But this year, September’s traditional ways, of longer, warmer days gradually yielding to shorter, cooler ones, seemed to have been at least partially reversed.

The decline in daylight marched inexorably on. But that wasn’t so of the temperature. On only its second day, September offered a high reading at Reagan National Airport that was, for the time of year, laughably low: 65 degrees.

Combined with the day’s coolest temperature, the entire day was ranked by the National Weather Service as 15 degrees below the normal figure for Sept. 2.

FREDERICK, MD -SEP 30: September came to an end with dryer, warmer weather than it started. This is not the way it usually works, but it is the way it sometimes does.(Photo by Michael S. Williamson/The Washington Post) (Michael S. Williamson/The Washington Post)

The Sept. 2 chill came two days before Labor Day, which many choose to recognize as the traditional end of summer. It arrived 20 days before the autumn equinox, which is frequently recognized as the end of summer.

Whatever else might be said about Sept. 2, it was totally unsuited to summer.

It seemed however, to be a proper choice to represent the first half of the topsy-turvy September of 2017.

As it turned out, Sept. 2 was one of 10 days in September’s first 15 that was cooler than normal. Then warm weather followed.

A single day in September seemed to serve as a hinge for the month, , marking the apparent swing from premature autumn to resurgent summer.

This year that fateful date was September 12. Before it came six consecutive days on which the daily average temperature was cooler than normal.

After Sept 12, according to National Weather Service figures, every day but Saturday was warmer than normal.

In fact, in a vivid example of September’s statistical oddity, some of the days of late September could easily have passed for summer. Of the four days from Sept. 24 to Sept. 27, three had readings above 90. Because the warm days were comparatively warmer than the cool days were cool, the month’s average temperature was above normal.

In another distinction of September’s second season, during the entire last half of the month it did not rain on anyone’s picnic, parade or protest. (And demonstrators a-plenty gathered beneath those droplet free skies.)

From September 15 through Saturday, not a trace of rain fell into the gauges at National.

Without hurricanes, tropical storms or the remnants of either, the total for the month was 1.43 inches, less than 40 percent of Washington’s normal reading.