Autumn temperatures in the United States will be warmer than normal across much of the country, except for cooler than normal over northern New England, the Southeast, and the Pacific Northwest.
Autumn rainfall will be above normal over the Northeast and mid-Atlantic states, across the Deep South, from the Lower Lakes through the Upper Midwest and Heartland, and across the Pacific Northwest and southern California; it will be near or below normal elsewhere.
In Canada, autumn temperatures will be warmer than normal from southern Ontario through the Prairies and across the Northwest Territories and the Yukon and near to below normal elsewhere.
Autumn rainfall will be above normal from the southern Maritimes through southern Ontario, across the Prairies and southern British Columbia, and over the Northwest Territories and below average elsewhere.
September Forecast: Start of Fall Brings a Mixed Bag for All!
Throughout the month of September, temperatures will mainly be near or below normal across the northern half of the U.S. and above normal in the southern half, Alaska, and Hawaii. Near- or above-normal temperatures will be found across southern Ontario, Yukon, and the Northwest Territories, with below-normal temps elsewhere. Precipitation is expected to be below normal across Florida, Texas, Oklahoma, and Hawaii and near or above normal elsewhere, while near- or above-normal precipitation is expected across all of Canada.
October Forecast: Cool Air Keeps Away
October temperatures will be cooler than normal in Florida, the Southeast, and the Deep South but warmer than normal elsewhere in the United States. Precipitation will be above average from Maine to Georgia and westward through the Appalachians, with a tropical storm and heavy rain possible across the Deep South late in the month. It will be drier than normal in most other locations.
In Canada, October temperatures will be warmer than normal across much of the country. Precipitation will be above normal in southern Quebec, southern British Columbia, and the Northwest Territories and generally below normal in most other areas. A hurricane may impact Atlantic Canada around the middle of the month.
What About Winter?
Looking ahead to the winter forecast, we’re monitoring several different factors. Of note, the La Niña that has been in place for the past 2 years has been expected to become more neutral as the year goes on. However, the latest indications are that the current La Niña could persist all the way through the upcoming winter. La Niña conditions rarely last for three consecutive winters, so this is a setup that we don’t often see.
The Atlantic Multi-Decadal Oscillation (AMO) remains in a warm phase, while the Pacific Decadal Oscillation (PDO) is currently in a negative, or cool phase. Oscillations are linked ocean–atmosphere patterns that influence the weather over periods of weeks to years.
We’re also monitoring the Sun, as sunspot activity has dramatically increased during the past 6 months and now is at its highest level since 2015. The relationship between increased solar activity and the future phase of the stratospheric winds near the Equator (known as the QBO) could lead to the polar vortex becoming displaced from the North Pole. This would open the door for some cold shots across the eastern United States and Canada this winter.