The polar vortex is stirring up, bringing the earliest hints that the weather is changing as autumn has officially arrived.
In the short term, this means gradual cool-downs and a more active storm track across the northern United States. But not everywhere will feel the chill quite yet. In Western New York, highs are still expected to reach into the 80s this week, with overnight lows mainly in the upper 50s.
Parts of northern New York have similar predicted highs this week, with several overnight lows predicted to dip into the 20s and 30s. In turn, some areas may have already felt their first frost of the season, while others may see it this week.
When will cold air move in? Average first frost dates in New York
The Climate Prediction Center’s outlook shows well-above-normal temperatures across New York through December, although the transition to La Niña could change that, bringing more frigid air to the state in December.
Much of the state can expect to see its average first frost within a month. According to the National Weather Service in Buffalo, Watertown already marked several frigid days last month – the coldest dropping to 32 degrees on Sept. 20.
According to data dating back to 1900 from the National Weather Service, here is when each major city sees its average first frost, or temperatures dipping below 32 degrees.
Rochester
Buffalo
Syracuse
Albany
Poughkeepsie
Binghamton
New York City (Central Park)
What is the polar vortex?
The polar vortex is a swirling mass of frigid air high in the atmosphere, always present near the Arctic.
Its strength and position shift with the seasons, according to the National Weather Service. When the vortex is strong, the coldest air tends to stay near the North Pole. When it weakens or wobbles, pockets of that cold air can sometimes spill south, which can contribute to extreme winter storms or prolonged cold snaps in the U.S.
It’s important to note that the polar vortex doesn’t directly control U.S. temperatures — it sets the stage and reflects broader seasonal shifts in the atmosphere around the globe.
How much cold actually reaches New York, the Northeast or other parts of the country depends on other atmospheric patterns, like the jet stream and storm systems. Colder air could eventually move into parts of the U.S. as the vortex shifts, but that doesn’t mean immediate blizzards or Arctic outbreaks — it’s simply a sign that the atmosphere is gradually transitioning toward winter.
Over the longer term, forecasters will watch whether the vortex remains stable or weakens later this fall. A weaker vortex increases the likelihood of Arctic air reaching the U.S., while a stronger vortex generally keeps the chill locked farther north. In other words, the polar vortex signals potential cold approaching, but does not guarantee a brutal winter.
What does the polar vortex look like right now?
Zonal winds — which track west-to-east wind speeds circling the Arctic at stratospheric levels — are just above 10 meters per second as of Tuesday, Sept. 30. That’s fairly weak but typical for the start of autumn.
Over the next several weeks, forecasts show the winds steadily strengthening to 15–20 m/s, a normal seasonal ramp-up as the polar night sets in. Stronger winds generally keep the coldest air locked near the pole, meaning gradual cooling across the U.S., while the most frigid air sits near the pole.
Even as the vortex strengthens, it doesn’t directly push cold air south. This seasonal strengthening simply correlates with autumn weather patterns; it does not cause them. Essentially, the vortex sets the stage rather than controls temperatures.
When the polar vortex weakens or is disrupted — sometimes during a rare event called a sudden stratospheric warming — the jet stream can dip south, allowing Arctic air to reach parts of the U.S.
Contributing: USA Today network
This article originally appeared on Rochester Democrat and Chronicle: Polar vortex stirring as fall arrives. Here’s when to expect first frost in NY
Reporting by Victoria E. Freile, New York Connect Team / Rochester Democrat and Chronicle
USA TODAY Network via Reuters Connect
