Extreme Temperature Diary- Thursday September 2nd, 2021/ Main Topic: U.S. Average Temperature Fall Forecast

Dear Diary. The main purpose of this ongoing blog will be to track global extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉

Main Topic: U.S. Average Temperature Fall Forecast

Dear Diary. Welcome to boreal or meteorological fall if you live in the United States, or the three months that are September, October and November. It’s time for me to make another attempt at a forecast for average seasonal temperatures in the U.S. This forecast will be very broad and not specific for any one state comprising the continental United States (or lower 48 states).

I’m not forgetting about awful flooding and devastation left by Ida and California’s fires. I’ll have plenty of notes on these climate crisis events after our fall forecast.

So how will boreal Fall 2021 stack up compared to long term temperature averages across the United States? Will we continue to see the climate crisis signature of warmer than average conditions? Let’s try to make a forecast as usual at the start of a new season.

So how did the forecast work out for Summer 2021? Here is a link to the post for that forecast:

By September 7th the National Center for Environmental Information will finish their assessment for Summer 2021, so our verification is not complete as of June 1st. Let’s do fill in ranking numbers with 1 being the coldest and 127 warmest for a verification for 2021 months through July, which have already been assessed:

I’ll complete the Summer 2021 verification for this post around September 7th when NCEI processes their numbers:

And here is that verification: The ranking for Summer 2021 verified at 1, or 127th coolest since 1895. That’s right, we just experienced the hottest summer on record, average wise, across the lower 48 states.

Here are my two cents for a broad, rough forecast for the U.S. for Fall 2021, which I guarantee to be cooler than this past summer, of course, as the amount of daylight decreases across the Northern Hemisphere. First, I like to look at water temperature anomalies surrounding North America just before the start of a season to get a sense of how much potential heat can be added to the atmosphere across the continent. Here is what we see:

Just like at the beginning of summer we see some cool pockets of water mainly off the West Coast with some on the Gulf, but very warn anomalies on the East Coasts. These look like they will offset each other, or be neutral factors. The La Niña that has been present for the last year has become neutral and is also a neutral factor.

Second, I like to look at the strength of the Hudson Bay low or polar vortex at the start of any season:

Here we see that a Hudson Bay vortex, or low, has not formed yet. During the summer Canada had very warm temperatures since the Hudson Bay vortex did not appear much, if it formed at all. Here we have a positive factor.

Here is the National Weather Service forecast for Fall 2021:

I can’t argue with this NWS forecast. Once more the south-central states may turn out to be the relative cool spot.

Overall, Fall 2021 will probably verify above average looking at trends from the rest of the planet.

Last, we can get another clue looking at prior National Center for Environmental Information ranking and temperature record count data. For this I like to drag out that “Record Scoreboard” (updated through 8/31/2021):

Notice that after 2-5 months of above average conditions we have been seeing a below average month. For the spring May was that slightly cooler than average month. Summer was broiling hot. We are due for a cooler than average month after September. It’s cringeworthy to think that once we see another strong El Niño these cool months will be all warm with our blue colors disappearing from my charts.

Two out of the three fall months should be above average, but I doubt that any will approach a top ten ranking. Either October or November may see a colder than average ranking below 63, but of course I can’t tell which one. (Here are avg. rankings per year for the lower 48 states since 1895):


Not all seasons in the near future will see above average temperatures, but seasonal forecasters are beginning to ”chuck it,” discounting colder than average scenarios due to carbon pollution.

Again, here are all seasons ranked for the last decade:

Here is my bottom line forecast for Fall 2021:

“I think that this fall will be ranked above average. Carbon pollution is definitely making below average seasons more rare. I’m going to forecast that the Fall 2021 ranking will be around 95 + or – 10,  with above average confidence given all of the factors on this post. Given the forecast anomalous warmth, more serious climate crisis events, such as those occurring across the United States on September 2nd, will be quite likely this fall.

My forecast for Summer 2021 of a ranking of 80 was way too cool since last season should come in at least in the top five once NCEI processes data by September 7th.

Notice that the past six summers had a ranking at or above 70. The big El Nino event of 2015/16 really spiked global temperatures as well as those for the U.S. My fall forecast for 2021 is for relatively warm conditions similar to that of most of the last ten falls. We will see.

As of 2021 the top ranking for any month or season would be 127 since climatological rankings for the United States started in the year 1895.  I think that this fall will be ranked at least as high as 85. Carbon pollution is definitely making below average seasons more rare. As stated, I’m going to guess that fall of 2021 gets ranked around 95 + or – 10,  but with above average confidence given all of the factors in this post.

We will see how this forecast pans out around December 7th, 2021.

Here is some August 2021 climatology:

Here are more notes on the remnants of Ida:

Here is more climate and weather news from Thursday:

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)

Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:

(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.) 

Guy Walton “The Climate Guy”

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