Is the polar vortex splitting? Will Arctic cold hit the US in November?

What is being shared

On November 2, Men's Journal ran the headline "The Polar Vortex Is About to Break Down 3 Weeks Earlier Than Ever Recorded, and the East Could Feel It by Thanksgiving." The article blocks automated readers, so we checked its headline, which is what people are sharing, and the forecast it points to.

That forecast is Severe Weather Europe's, published October 28 and updated October 29: "a reversal in the current event is centered around Nov 4th, and would break the record for the earliest SSW on date by at least 3 weeks (Nov 28th)." SSW is a sudden stratospheric warming, explained below. Its maps show the vortex splitting into "two main Polar Vortex cores, over Siberia and the Atlantic."

Read together, the headlines sound like a cold wave is scheduled for the East by November 26. The forecasters themselves say something narrower: the vortex high above the Arctic is about to weaken at a record-early date. Where the cold goes afterward, if anywhere, is a separate question.

What the data actually shows

The standard measure is the wind about 19 miles up (10 hPa) averaged around the 60°N latitude circle. In winter it blows from west to east; a major sudden stratospheric warming is counted when it reverses to east to west. NASA's daily file, which we read on November 2, had that wind at 12.5 meters per second (about 28 mph) on October 31, the last measured day. The lowest ever recorded for that date, in NASA's record back to 1978, was 11.3. The average is 24.3.

The forecast part of the same file drops to 2.6 on November 3, 0.6 on November 4, and goes negative, -0.5, on November 5, staying negative through November 11, the end of the forecast. Those numbers are from a weather model, not measurements. The reversal is forecast, not observed.

Severe Weather Europe reported that model ensembles disagreed on how sure it is: the European ensemble "already shows a reversal with a 96% chance," the American GEFS 71%, and the AIFS ensemble 37%. NOAA's own stratosphere team keeps the record of major warmings since 1958; the earliest it lists is November 1968, dated November 27, 28 or 29 depending on the dataset, and one dataset adds November 30, 1958. A reversal on November 5 would beat that by about three weeks. Our analysis of 31 past events has what happened to US weather after each.

What NOAA's outlooks say for the US

NOAA's Climate Prediction Center, which issues the official US outlooks, is watching the same event. Its updated November outlook, issued October 31, says model forecasts point to a possible sudden stratospheric warming next week: "A November SSW is very rare, and should this occur, impacts can be seen for up to 2 months." Those effects usually show up as a negative Arctic Oscillation, it says, and that pattern is already in the models. It says that adds uncertainty for the eastern US, where SSW effects "compete with those from El Nino."

Even so, the updated outlook expanded the area favored for above-normal temperatures, "reaching further south and covering more of the Southeast," with 60 to 70% odds over the Northern Plains and Upper Mississippi Valley. The discussion describes only above-normal and equal-chances areas for the lower 48.

The shorter outlooks, issued November 2, point the same way. For November 8 to 12, above-normal temperatures are likely across the West and north-central US, with odds above 80% in the Northern Rockies and Northern High Plains; in the lower 48, below-normal is favored only over parts of the Southeast, under a trough. For November 10 to 16, "above normal temperatures are favored across most of the CONUS," least likely across much of Florida.

The week 3 to 4 outlook, issued October 30 for November 14 to 27, says "a rare November stratospheric polar vortex disruption is unfolding, with forecasts indicating a transition into a major sudden stratospheric warming (SSW) in a week." It still favors above-normal temperatures along the West Coast and across the northern tier, with equal chances of above, near or below normal in the Southeast and Southern Plains. Those are odds, not promises, and the next week 3 to 4 outlook comes on November 6.

What AccuWeather says

AccuWeather's October 30 story is headlined "No frigid air coming to US in November despite polar vortex being on the move." Its reasoning: "there is one big problem with the polar vortex event this time -the air in northern Canada is not all that cold to begin with." Senior Meteorologist Brett Anderson said: "This time, what true cold air exists in the pattern will be directed to Siberia, rather than North America."

It does expect temperatures to "trend lower in parts of the U.S. later during the first and second weeks of November," from storms forming overhead "rather than a bitterly cold blast," and says the pattern "may cool a bit more during the second half of November." Senior Long-Range Meteorologist Joe Lundberg said the jet stream's blocking pattern "may break down enough to allow some chillier air episodes to move southward into the U.S." in the latter part of November and December. He added that ski resorts open for Thanksgiving in the East may lack snow and the cold air to make their own. That is a forecast of a cooler, wetter pattern, and it is AccuWeather's, not ours.

What is confirmed, and what is not

Confirmed: a record-early disruption is forecast by the models, NASA's daily data shows the winds already about half their average for the date (12.5 meters per second against 24.3 on October 31, close to the record low of 11.3), and NOAA's forecasters call it rare and are factoring it in. If the reversal happens on November 5, it would be about three weeks earlier than the 1968 event, which is what the headline says.

Not confirmed: that the East will "feel it by Thanksgiving." No NOAA outlook favors below-normal temperatures for the eastern US in that window; the Southeast and Southern Plains are at equal chances for November 14 to 27, which means the forecasters don't lean either way. AccuWeather's forecast is cooler and wetter, not frigid. None of the NOAA outlooks we read (6 to 14 day, week 3 to 4 and monthly) describes an Arctic outbreak for the lower 48 in November.

Also not yet confirmed: the reversal itself. As of the last measured day, October 31, the wind was still blowing west to east. Any story saying the vortex has already split is ahead of the data.

How a sudden stratospheric warming works

The National Weather Service describes the polar vortex as "a large area of low pressure and cold air surrounding both of the Earth's poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter." NOAA's Climate.gov explains that the stratospheric part is "occasionally knocked off kilter when especially strong atmospheric waves in the troposphere break upward into the stratosphere." Then "it may wobble, slide off the pole, split into several lobes, or" in the most extreme cases, temporarily reverse direction. The spike in stratospheric temperature that goes with it is why it is called a sudden stratospheric warming.

What happens next is the uncertain part. Climate.gov says that "in the weeks following the stratospheric upheaval, the polar jet stream will often develop a wavy shape," bringing wintry conditions farther south than average under its troughs. NOAA's Amy Butler told Climate.gov in 2021 that the disruptions happen "on average about every other year in the Arctic" and that "some part of the mid-latitudes will ultimately experience a cold air outbreak." Which part is the question: the research links them to cold outbreaks in "the United States or Eurasia a few weeks later." This year, AccuWeather expects the cold to go to Siberia.

Two more things make this event unusual. It is November, so the Arctic has had less time to build up cold air; and NOAA's October 8 ENSO discussion says a strong-to-very strong El Niño is likely through January to March 2027, with sea surface temperatures in the Niño-3.4 region 2.1°C above average. The Climate Prediction Center says El Niño "remains the dominant teleconnection" for November and that the two drivers pull in different directions over the eastern US. That is why NOAA's outlooks lean warm with lower confidence rather than cold.

What it means for your home

Nothing in these forecasts calls for buying anything. The National Weather Service's own advice is the right size for it: "there is no cause to be alarmed when you hear about the polar vortex, but you should be prepared for colder temperatures." Winter is coming regardless, and the mild start NOAA's outlooks favor is the easy time to get ready.

Start with our winter storms page, which lists today's NWS watches and warnings by state, and the winter storm kit builder, which sizes Ready.gov's list to your household. Our winter storm preparedness guide covers the rest. If you heat with a space heater, read the space heater safety guide before our space heater comparison.

• Alerts: sign up for your community's warning system and keep a NOAA Weather Radio; our winter storm warning page explains what each alert means (Ready.gov, NWS)
• Carbon monoxide: alarms on every level of the home and outside sleeping areas, with battery backup, tested every month (CPSC)
• Furnace: have a professional inspect fuel-burning heating systems, chimneys, flues and vents every year (CPSC, CDC)
• Supplies: enough to stay home for several days without power, including medication, with flashlights, extra batteries and a battery-powered radio (Ready.gov, NWS)
• Heating fuel: refuel before you are empty; deliveries may not reach you for days after a storm (NWS)
• Pipes and drafts: insulation, caulking and weather stripping, and know how to keep pipes from freezing (Ready.gov)

What not to do

Don't heat your home with a gas stove or oven. Ready.gov says it "increases your risk of carbon monoxide poisoning." Use generators and grills only outdoors; keep generators at least 20 feet from windows, doors and attached garages.

Don't plug a space heater into an extension cord or power strip, and don't leave one running while you sleep. CPSC says to keep portable heaters at least three feet from anything that can burn, and estimates they were involved in an average of 1,600 fires a year from 2020 to 2022.

Don't treat the headline as a forecast for your town. Check the live alerts page and your local forecast on weather.gov when cold does arrive. We will update this check as the data comes in.