BETHESDA, Md. - Fall is arriving in the Washington, D.C. region with a potentially rare large-scale weather pattern taking shape across the Pacific.
What we know:
A strengthening El Niño is expected to become exceptionally strong, potentially record-breaking, during the fall and early winter months. That could play an increasingly important role in the weather pattern across the entirety of the United States, including in the D.C. region.
For our region, the overall signal currently favors a warmer-than-average fall, but that does not mean three straight months of summer weather hanging on. Periods of cooler weather, sharp cold fronts and chilly mornings will still occur and become more common as the season progresses.
Wetter-than-normal conditions are favored as well, with coastal rainstorms becoming more likely as the fall goes on.
The biggest questions are: how quickly the region transitions from summer warmth to more sustained fall chill, and when can we expect the first signs of winter to appear?
SEPTEMBER: A Slow Start to Fall
While fall will eventually settle in, the summer pattern will occasionally fight back this September.
September has already started quite warm, including a 98°F day to kick off the new month here in Washington, D.C., just 1°F off a record high for the day.
Extended guidance suggests that we will stay on the warmer side of average through the middle of the month, as the summer pattern fights shorter daylight and a lower sun angle as the month goes on.
That said, the transition toward fall should become more noticeable as the month progresses. Various models, including artificial intelligence-enhanced weather modeling, are suggesting the first taste of true fall weather may come right around the official start of autumn, which falls on September 22 this year.
Still, with the strengthening El Niño helping power a stronger-than-average subtropical jet stream, humidity will likely be a bit slower to trail off than it is during a more typical fall season, and that means more warm to mild days, and particularly evenings, ahead.
Precipitation-wise, we expect that September will likely end up around or perhaps even a touch below the seasonal average (3.93") despite the strong start to the month with over 1.5" already in D.C. But the typical El Niño wet pattern does not typically settle in until we get a little deeper into the fall season.
TROPICS: Staying Quiet
We are likely to set a record for the latest first hurricane since the satellite era of hurricane tracking began (1966).
Through the first week of September, there has not been a single Atlantic storm that has reached hurricane status.
The average date of the season’s first hurricane is around August 11, so we are running about a month behind schedule there. It is, in fact, the first time since 2013 that we have gone this deep into the hurricane season without a single hurricane named. We have, however, had five named tropical storms already.
That being said, hurricanes are more common during the early second half of the hurricane season than the first half, with September averaging about 2.4 hurricanes per year, while October averages 1.5 hurricanes per year.
Since the satellite era of hurricane tracking began, we have never had an Atlantic hurricane season go by without at least one hurricane. If we make it until September 12 without a named hurricane, it will officially be the latest on record that a hurricane has developed in the satellite era.
Two seasons, 1907 and 1914, are on record as being the only two without a confirmed hurricane, though these do, of course, predate the satellite era when not landfalling storms were harder to track the intensity of. Still, all indications are that heading into the second half of this hurricane season, this may end up being one of the least intense hurricane seasons in recent memory.
OCTOBER: Wet, But Mild Leaning
The most recent fall outlook from NOAA’s Climate Predication Center slightly favored a milder-than-average fall in the Mid-Atlantic region, and for much of the country.
October is when the weather pattern should begin to feel substantially more autumn-like across the D.C. region. In most years, this does naturally happen.
Average highs in D.C. to start the month are comfortable at 75°F, while by the end of the month they have fallen to just 64°F.
So how do we expect this October could differ from a more typical October in the DC region? I think it’s twofold: a wetter month, but also a milder month, particularly during the second half.
By this point, the strengthening El Niño is expected to be much more established. NOAA's ENSO outlook indicates a greater than 90% chance of a very strong El Niño during the fall and winter, with peak intensity expected sometime between October and December. For the Mid-Atlantic, that could translate into an increasingly active storm track at times, leading to a wet outlook. October averages 3.66" of rainfall in D.C., and it is a number I expect we’ll surpass in D.C.
The last two very strong El Niño events produced 3.04" (2015) and 4.04" (1996), respectively.
Temperature-wise, while we will absolutely see periods of occasional fall chill as the shorter daylight days make them more common as the month goes on, an active subtropical jet will occasionally bring us a taste of some tropical warmth and humidity even through the end of the month.
During the 1996 very strong El Niño October, seven of the last final days of the month exceeded 70°F, including an 82°F day on October 30 of that year. We are not talking extreme heat, just days unusually mild for that time of year.
LEAF PEEPING: How Will the Foliage Look This Year?
While peak fall colors in the DC region rarely see extreme deviations from the average, they could be a little delayed this season due to an expected miler fall season.
The 2026 fall foliage season could be a slow and gradual show across the Washington region, as the timing of cooler weather plays a major role in when the leaves do start to change.
A warmer-than-average fall would generally favor a later start to widespread color, especially across the lower elevations around Washington, D.C., and the immediate suburbs. However, periodic "chilly burst" during both October and November should still help push the trees toward their peak colors.
Look for the first noticeable changes to develop in the higher elevations and northern portions of the region during early October, with color gradually spreading south and east toward the D.C. area later in the month and into early November.
Our favored timing:
- Early October: Limited color, primarily in higher elevations.
- Mid-October: Increasing color across the mountains and northern Mid-Atlantic.
- Late October: More widespread color across the DC region.
- Early November: Potential peak period for the immediate Washington area.
- Mid-November: Peak color shifts southward, with very fast leaf drop this year.
Tree stress was very high for most of the spring and summer months in the area, thanks to a drought. However, the drought has seen immense improvement since the middle of the summer in our region, and late-season rainfall can help the trees produce some vibrant colors by the middle of fall. A key factor that we need to monitor is our mild October outlook.
If the month stays consistently warm and features only minor cold shots, and particularly if evening lows are elevated for most of the month, the color change can be both delayed and more muted. You want warm afternoons and chilly nights through the month of October to really bring out the best of the fall colors in our region.
Compared to an average season, we do think we could potentially see a later-than-average start, but still plenty of opportunity for a colorful fall during the peak.
NOVEMBER: Sneaky Shots of Winter Cold
DC’s first freeze has fallen in November each of the last fourteen years here in DC
November is where the atmosphere could begin making a more noticeable transition toward winter. In a typical November, our average first freeze generally comes our way during the middle third of the month, with November 17 being the average date.
As noted in the October outlook, we expect that the latter part of October may end up on the milder side of things. This could linger into early November, and we would not be at all shocked to see some 70s, if not even, as was the case during the 2015 very strong El Niño November, some lower 80s.
It’s the latter two-thirds of the month when some of the first signs of winter could show up, and perhaps even catch the region off guard by how intense some of the cold shots can be.
Once again, the reason all goes back to the intensity of the coming El Niño. By November, the exceptionally strong El Niño signal is expected to be firmly established. NOAA's latest outlook showed very strong El Niño conditions becoming increasingly likely throughout the month, with the event potentially reaching historic strength.
As noted in our tropical section above, while these extreme El Niño events correlate well with a below-average Atlantic hurricane season, they have the opposite impacts in the Pacific, where the warm waters often lead to intense typhoon activity.
During the 2015 very strong El Niño, the western Pacific saw at least one named storm develop every single month of the year, with 18 total typhoons, with half of them reaching super-typhoon status. It remains the fourth most intense typhoon season by the Accumulated Cyclone Energy (ACE) index. But what do typhoons have anything to do with our weather here in D.C.?
When a powerful typhoon in the western Pacific turns north and northeast, it can interact with the polar jet stream, as it floods the northern latitudes with milder air the storm drags northward from the tropics. This can send a ripple of energy through the atmosphere that travels eastward across the Pacific, which then impacts the pattern downstream.
In the Northern Hemisphere, mid-level winds travel west-to-east for the most part, placing the United States downstream of these impacts. While it does not happen with every typhoon that takes this track, it is a pattern impact that is well noted in the field of meteorology.
Think of it like a domino effect:
- A typhoon turns northward in the West Pacific.
- The typhoon holds onto its strength longer than normal, due to the warmer waters.
- The storm gets into the northern latitudes, where it disrupts the polar jet stream, which is gathering strength at this time of the year ahead of winter.
- This buckles the jet, with a deep trough developing as the low pressure associated with the typhoon interacts with the region.
- Downstream, a ridge then develops across Alaska and/or the western United States, what it known as a positive phase of the Pacific-North American pattern, or a +PNA.
- This leads to trough developing over the eastern half of the United States, which can lead to stronger than typical cold air transport out of Canada into our part of the country.
Now, these surges of cold tend to be rather short-lived and not sustained for long, but they can surprise us with earlier than expected cold, frost, and even snow showers and flurries from the Great Lakes. So it is certainly something we will have to monitor during the month of November, when it may still be fall in the States, but much of Canada is already seeing strong winter air masses start to gather and develop.
As for rainfall, we expect that November will likely see similar rainfall to October and remain wetter-than-average for the D.C. region. With the polar jet stream gathering strength ahead of the winter months, and the subtropical jet remaining strong and moisture-heavy, their occasional interaction will likely power some decent rainstorms along the East Coast during the month.
WINTER: An Early Look
While our winter outlook will be released later in the fall, we did offer a bit of a preview of what we believed this winter would bring earlier in the summer when we spoke about the forecast for the Super El Niño, and as of today, our thoughts really have not deviated too much from those initial ones we made.
These include:
- Occasional strong cold shots, but an overall mild-to-warm winter compared to average.
- A wet winter, with higher chances for rainfall.
- Not as many snow events as a typical winter, less small-scale snow events.
- Still, because of the increased moisture present, if a push of cold is timed perfectly with a storm from the south (like January 2016 was) we could see a bigger snowfall. So while overall snow potential for this winter is lower...the blizzard risk is greater than a typical winter. Lower floor, but higher ceiling type winter. These would be most likely between mid-to-late January and then through February.
The recently released Farmer's Almanac seems to have taken a very similar outlook.
Stronger El Niño events tend to be easier to forecast in terms of the winter outlook because of their intensity and their impacts on the pattern.
The biggest question mark will remain, likely every winter: will cold and moisture meet up in a timely enough fashion to provide us with at least one major snow event. It only takes one to make a winter memorable, after all!
The Source: Information in this article is from FOX 5 DC's weather team.