TheClimateChanger

Well, maybe sobering was too dramatic of a word. Certainly, the warmer minima are a blessing for farmers completing their fall harvests. With that said, it does raise important questions about the speed and extent of the environmental changes occurring since the plant and animal life in a region may have evolved in a manner that depends on frosts or freezes occurring by a certain date, or temperatures reaching a certain level of coldness over the winter [i.e., potentially to kill off parasites, which may harbor disease]. Although just outside this subforum, if we look at Hagerstown, Maryland, we see sub-40F lows in the month of September are now rarer than subfreezing lows were historically. That's a significant change. Since 2000, only year has had a low temperature less than 40F (2020, when it dropped to 38F). Conversely, 19 historical Septembers had lows at or below freezing. However, this has not occurred since 1974. Whereas in the 2010s, three separate years had absolute minima in the 50s, in the 1940s, three separate years saw minima in the 20s. Warmest absolute monthly minima Coldest absolute monthly minima [showing all years at or below the freezing mark] Like central Pennsylvania, many past years had mean monthly minima less than the coldest temperatures observed in recent years. In fact, if we look at 2018's absolute low of 54F at Hagerstown, fully 52 years had mean minima less than or equal to this value in the month of September. And allowing for rounding, fully 57 years had mean mimima less than 54.5F.

With a couple days left in the month, cold air has been lacking in many locations in New England with absolute monthly minima in several locations among the warmest of record. The warmer nights are certainly a blessing for farmers completing their fall harvests. Burlington, Vermont Mount Washington, New Hampshire Caribou, Maine Worcester, Massachusetts Some of these locations have observed several Septembers where the monthly mean low temperature was roughly the same as or colder than 2023's absolute coldest night. Most notably, the year of 1963 saw a mean low at Burlington, Vermont of 40.2F, or nearly 5F colder than 2023's coldest of 45F, and also a mean monthly low of 46.9F at Worcester, Massachusetts, a little more than a degree less than 2023's coldest of 48F. Burlington, Vermont Worcester, Massachusetts

I've been following this for awhile, and it's been interesting to see the dense smoke interacting with the lower sun angles over the high latitudes. Nuuk, Greenland was very dark at midmorning a few days ago, and I saw many in Atlantic Canada observed strange, pale sun through the nearly opaque layer of smoke. Even in the UK, the sun has been significantly dimmed behind the pall of smoke. I wonder if the limited solar radiation will help to promote some early season cold air masses.

Looking at graphs like this, it should be apparent that this is Canada's version of Australia's Black Summer of 2019-2020. Will be interesting to see whether this results in a miniature volcanic winter in the Northern Hemisphere. Smoke from Australia's Black Summer fires are known to have cooled the earth, particularly in the southern hemisphere, and possibly increased the chances of that multi-year La Nina: Smoke from the Black Summer wildfires in Australia impacted climate, high-altitude winds of the Southern Hemisphere (phys.org) A recent study found wildfire smoke and volcanic emissions have offset 20% of the warming which would have otherwise occurred since 2015: Smoke from volcanoes and wildfires have a parallel cooling effect, but it won’t do much to quell global warming | Enterprise Will be interesting to see whether this has any sort of lasting impact on the global, or regional, climate. For the record, there have been a number of intense outbreaks of pyroCb sufficient to loft a significant quantity of soot and smoke into the lower stratosphere over the course of the summer.

Elkins, West Virginia Warmest Absolute Low Temperatures Coldest Monthly Mean Minima Wow!

Man, I'm a sucker for statistics. But even I am taken aback sometimes. It's crazy seeing how the coldest temperatures observed in many locations for the entire month of September in recent years are now sometimes roughly the same or even warmer than the mean monthly minima from many historic Septembers. I know many of you said people don't care about low temperatures, but to me stuff like this is just plain sobering to see. It's like this at many places too. Harrisburg - warmest absolute monthly minimum temperatures [Note: It dropped to 50F today, which is not yet reflected in this] Harrisburg - coldest mean monthly minima

Grand Forks has dropped as low as 36F this month, which, should it hold, ties for third warmest monthly minimum behind the 40F lows observed in September 2021 & 2019. However, in 1893, the low temperature was as cold as 11F on the 27th, and 14F on the 26th, just to give an idea of how cold it can be this time of the year in the upper Midwest and northern Plains. Many a hardy palm tree would have perished in the September 1893 cold snap, I would think. Interestingly, quite a few historic Septembers in Grand Forks had mean monthly minima roughly the same, or colder than, the absolute coldest September low temperatures in several recent years.

With only a couple days left in the month, it appears almost certain that many areas in the Midwestern United States will see one of the warmest absolute minimum temperatures ever recorded in the month of September in 2023. The lack of any early season cold is a blessing farmers and sensitive plants (including hardy palm trees). Minneapolis, Minnesota Chicago, Illinois Milwaukee, Wisconsin Des Moines, Iowa Grand Forks, North Dakota Marquette, Michigan

And yet we have these crazy yinzers on Reddit who think it’s some sort of achievement not to run the heat by October 1: https://reddit.com/r/pittsburgh/s/1ePk1TxQI5

Purple sun over Atlantic Canada today from dense wildfire smoke aloft.

Interesting pattern. Unless the Canadian wildfires are under control by then, dense smoke looks possible as well.

Saltwater intrusion a significant concern for the New Orleans area, as rising sea levels and severe drought are combining to enable the seawater to spread farther inland along the Mississippi. Of note, the gage level upstream at Memphis has fallen to -10.18 feet, and was as low as -10.29 feet earlier today (see graphic below). The forecast takes the level to -10.90 feet by October 10. This would exceed the low water record of -10.81 feet set last October. Previously, the lowest observed level was -10.70 feet, set in July 1988.

Faster than expected, that's been the theme for some time. I'm not surprised given the history of past climate changes on earth. The models are probably underestimating some of the synergistic feedbacks of climate warming.

Here was the weather on September 24, 1950. Perhaps the most notable thing is the temperatures, which are almost unfathomable by today's standards for the month of September. Erie Erie had a high of 48F, and a low of 46F. The comment states: "On the afternoon of the 24th, a dense layer of smoke aloft, together with a lower overcast of cloudiness, caused nighttime darkness so that floodlights were necessary for an afternoon ball game. The phenomenon is without precedent here and caused considerable alarm." Williamsport Williamsport had a high of 52F and a low of 39F. Further down in the monthly summary, the Weather Bureau observer left the following remark: "The most outstanding phenomena of the month was the rather complete obscuration of all sunlight and skylight for a period of two hours late afternoon the 24th due to a thick, high level smoke stratum from western Canadian forest fires. General atmospheric smoke remained till the month's end in a stagnating air mass over the region."

Also, of note, on yesterday's date 73 years ago, Black Sunday occurred in the Commonwealth. When I was looking up the history of wildfire smoke in the Commonwealth earlier in the summer with the seemingly near constant plumes of smoke, I came across this event from 1950. People were very perplexed, and many thought the world was ending or aliens were about to invade. Here are some reports from Bradford and Coudersport area. Bradford Landmark Society - The Day the Sun Went Out In Bradford - Bradford Pa History Historical Society Black Sunday: Darkness falls in the PA Wilds - Pennsylvania Wilds Some good eyewitness accounts on this site, with some even indicating stars were visible. This would suggest a large object eclipsed the sun outside of earth's atmosphere, perhaps giving some credence to the alien spacecraft theory. The official explanation today, however, is a pall of smoke from the Chinchaga firestorm in western Canada. darksunday (the-red-thread.net)

Interesting to see 1921 appear on several lists. That year seems like it was a little taste of the present climate in Pennsylvania, with hot summer months and high annual means as well. Wonder what happened to make it so warm that year.

With 5 days left in the month, the coldest temperatures observed so far are among the absolute warmest on record for the month of September across much of the Commonwealth. Frosty weather has been missing in action, even across the highest of elevations. Williamsport Bradford DuBois Harrisburg/Middleton Mount Pocono Philadelphia Scranton