Expect mild, dry weather into middle of October
Here in the Inland Northwest, after a warm summer, the weather will start turning cooler than normal by the middle of October. Moisture levels are also expected to increase as we have the cooler La Niña sea-surface temperature pattern in the south-central Pacific Ocean. Our snowfall should begin by the middle of November.
In the meantime, the rest of September and early October should be drier and a bit milder than normal. We’ll still have some showers and perhaps an isolated thunderstorm, but the big weather change should arrive toward the middle of next month.
If La Niña continues to hang on to life, snowfall totals for the winter should be near to slightly above normal. More details on that scenario later.
As far as the rest of the nation is concerned for fall, the Southwest, including Southern California, has been suffering from one of the worst droughts and fire seasons in history. High pressure has been holding on in the region and will continue to do so into early November. The chances for shower activity do increase in late November and December, but moisture totals should remain below normal through the end of the year.
In the north-central U.S., frosty temperatures are possible southward to Interstate 80 near the autumnal equinox, Sept. 22. This area will likely see above normal precipitation and cooler than normal temperatures during the fall. An early start to winter may also be on tap.
In the southern Great Plains, however, it looks drier and milder than normal until mid- to late October. Much of this region has suffered through one of the worst drought patterns since the 1930s. By late October or early November, conditions should start turning a bit wetter and cooler.
The cooler sea-surface temperatures will keep the northeastern U.S. generally wetter and cooler than normal. However, conditions should start turning drier and warmer than normal as the high pressure system expected over the central U.S. moves to the east later in the fall. Conditions should then turn colder and snowier, just in time for the holiday season.
Across the southeastern U.S., more showers and a few thunderstorms will persist. A tropical storm or hurricane is still possible through at least the middle of October. Near-normal weather is expected in November and December.