Late Summer Nights

Reader Gary alerted me to the fact that so far there's very little autumn color in the trees around Fairbanks, and this is indeed unusual for the date.  Prime season for autumn foliage is typically from late August to early-mid September in the central interior.  Webcam photos from today confirm the report:

(Goldstream Rd at Old Steese Hwy)

(View from Cleary Summit on the Steese Hwy)

(Nenana)

Unusually warm weather is undoubtedly the main cause for the anomaly, and in particular it's the absence of cool nights, I think.  Check out how persistently warm the daily minimum temperatures have been since mid-July.

Remarkably, there has only been one day with a low temperature below 50°F since July 9, and that was a mere 47°F on Sunday morning.  Compare this to the 1991-2020 normal, which dropped below 50°F two weeks ago and is already down to 45°F.

No previous year (since 1930) had less than 3 nights below 50°F by this point in the season, so the absence of overnight chill is unprecedented in the modern climate record.  Not surprisingly, then, the average minimum temperature since mid-July is easily the highest on record:

Besides the dramatic long-term trend, it's also interesting to see the loss of sub-50°F values on this chart in the last 10 years; it seems it was only a matter of time before a new high mark was reached in the series.

In contrast to the persistently mild nights, daytime temperatures have dropped off quite sharply in Fairbanks as the warm and dry fire-weather pattern gave way to cloud, rain, and high humidity.

It's the abundant cloud cover that is now keeping temperatures elevated at night, because the air aloft isn't particularly warm any more.

For those who look forward to the change of season, a glance to the north reveals the future: today saw the first snow of the season at Toolik Lake.

First snow of the year @Toolik pic.twitter.com/0iu2OU2D0F

— Dr. Amanda Young (@arctic_ubetula) August 23, 2023