Moody weather marks the end of summer’s peak at 8,800 feet above sea level.

Something happens this time of year. Perhaps it’s the subtle shift in the sun’s position in the sky, or the occasional morning in the high 40’s and not the low 50’s. Whatever it is, early-August marks the beginning of the change.

In modern western society summer begins June 21 and ends September 21. Around here, those numbers mean little. While June 21 feels like summer in earnest – the endless daylight, everything blooming, the insects and birds in full flight – late September is the heart of autumn here, not the beginning.

In late September the aspen trees are in their full regalia, donning their yellow caps. The mornings are crisp, and with few exceptions the high peaks have had at least one blanket of snow to cover the tundra and talus. Usually that snow melts off before real winter hits a month later, but there is no confusion about what season late September is here. It’s fall, the most beautiful and fleeting season there is.

In pagan societies, early August marks the halfway point between the summer solstice and the fall equinox. The pagans had a name for this time of year – Lughnasadh or Lammas. It marked the beginning of the harvest season, when the wheat and crops were ready to be picked.  Pick now, for the turn towards cold is eminent.

Dim evening light in the forest makes the river smooth.

In nature, the first evidence of the change can be found by looking toward the ground, at the ferns.  Aspens get all the glory, but the ferns lead the way. When the ferns go, a cold night – and the aspens – are not far behind.

There is a little hike near our home that loops underneath a pine and fir covered mountain. A stream runs thru the valley, and along this trail, where the cooler mountain air descends to the stream, there are perpetual cold spots. In the summer, one is likely to bump into a moose or a rabbit in these places, both seeking refuge from the baking heat of the day.

A few days ago on our walk, we saw our first yellow fern of the year. And then a little further on, in the very coldest spot in the entire valley, another and another.

The first yellow ferns of the year.

The ferns know. Another autumn has almost arrived. The season to saunter in golden leaves and climb frosty mountain peaks is around the corner.