Fall Weather Forecast 2020: September Brings Cool Weather East, Warmth West

Read the Latest Forecast for September 2020!

August 21, 2020
Autumn leaves in snow

As the days shorten and the leaves turn, we march closer and closer to autumn! Wondering what sort of weather the season will bring? Here’s a sneak peek at what to expect with our Almanac 2020 Fall Forecast.

‘Tis all a myth that Autumn grieves,
For watch the rain among the leaves;
With silver fingers dimly seen
It makes each leaf a tambourine.

–Samuel Minturn Peck, American writer (1854-1938)

September Holiday Forecast: Cool in the East, Warm Out West

Labor Day (September 7) marks the last hurrah of the summer season across the United States and Canada. Good news! The weather will mostly cooperate if you have plans for one last barbecue before autumn weather sets in. Most of the eastern half of the United States will be a bit on the cool side during September, although sprinkles will be few and far between. Showers will be more widespread from Texas to Arizona and northward to the Canadian border, although temperatures will be on the warm side in most of these areas. Parts of Alaska and Hawaii will also see showers.

Meanwhile, hot, mostly dry weather will be the rule from Washington down through California. Folks in Atlantic Canada and the Yukon and Northwest Territories will see a few showers, but elsewhere across the commonwealth, dry and cool weather will prevail.

For Patriot Day on September 11, showers will be the rule across much of the United States, although sunshine will dominate from the Heartland to California.

My favorite day in September is Grandparents Day (September 13). Whenever I get the chance, I train my grandkids to do to their parents all the bad stuff my kids did to me—revenge is sweet! The grandkids will have to do it indoors in most places in Canada and the eastern two-thirds of the United States, as rainy weather and cool temperatures will predominate. Most of the western states will see warmer, dryer weather; dry air of a cooler nature will prevail in Atlantic Canada.

Autumn mountains, NC

2020 Fall Weather Forecast Summary

Autumn, with its cool, crisp nights, warm wool sweaters, and endless amount of pumpkin-flavored foods, officially begins with the autumnal equinox on Tuesday, September 22.

September 2020

September will bring cooler-than-normal temperatures, on average, which will linger through the month in most places, although temperatures for the month will average above normal in Florida, from the Intermountain region and Arizona westward to the Pacific, in Alaska and Atlantic Canada, and from the Prairies westward to the Pacific and northward to the Yukon.

September precipitation will be on the heavier side from southern New England southward to Georgia, from Pennsylvania southwestward to Louisiana, and in the Desert Southwest, southern Alaska, Atlantic Canada, Quebec, and portions of the Yukon and Northwest Territories. It will be near or below normal elsewhere.

October 2020

Just when an early winter seems inevitable, October will roll in with milder-than-normal temperatures nearly everywhere—actually, make that “much warmer than normal” temps in the eastern two-thirds of the United States. But enjoy it while it lasts: As the leaves begin turning color and floating to the ground, above-normal rainfall will visit the Deep South and Southeast and range northeastward to New England, as well as predominate from central California northward through the Pacific Northwest. Most other areas will be dry or nearly so.

Autumn temperatures will be above normal in Atlantic Canada, southern Ontario, the Prairies, British Columbia, and the Yukon and below normal elsewhere across the Canadian commonwealth. Precipitation will be below or near normal in Ontario and the Prairies and above normal in nearly all parts of the other Canadian provinces.

A Preview of Winter Weather Ahead

Dare we even mention winter yet? (It is our job, after all.) Here’s a preview of what weather we’re expecting this year. For more, check out our new Winter Weather Forecast 2021!

As far as the upcoming winter goes, we will be entering Solar Cycle 25, which is expected to bring very low solar activity. Although low levels of solar activity have historically been associated with cooler temperatures, on average, across Earth, we believe that recent warming trends will dominate in the eastern and northern parts of the United States in the coming winter, with below-normal average temperatures limited to the western portion of the nation. Temperatures will average above normal in most of Canada, except for Atlantic Canada and the Prairies, where below-normal temperatures are expected.

As we move toward the winter, watch for any changes in the ENSO pattern (the El Niño–Southern Oscillation, which is based on temperatures in the Pacific Ocean), where we expect a weak La Niña to develop. If the La Niña were to be stronger, colder temperatures would likely prevail across the northern Plains and southern Ontario. On the other hand, if we instead have more neutral conditions or an El Niño, California would experience heavier rainfall while the Canadian Prairies would have milder temperatures.

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