BREAKING NEWS Baseball legend Hank Aaron passed away at the age of 86 Full Story

Polar vortex: Your questions answered

CNN's Jennifer Gray explains what is a "Polar Vortex" and what to do if you find yourself in very cold temperatures.

Posted: Jan 28, 2019 11:35 AM
Updated: Jan 28, 2019 11:45 AM


The coldest air in a generation is spilling out across the US thanks to a breakdown in the polar vortex.

The icy blast it's sending southward is the biggest visitor from the North Pole since Santa Claus. The gifts it brings, however, are chilling and generally unwelcome.

Seventy-five percent of the continental US will dip below freezing at some point this week, leading to record low temperatures across the country. CNN meteorologists Brandon Miller and Judson Jones answer a few pressing questions about this phenomenon.

What is a polar vortex? What distinguishes it?

The polar vortex, as its scary name suggests, is a circulation of strong, upper-level winds that normally surround the northern pole, moving in a counterclockwise direction -- a polar low-pressure system.  These winds tend to keep the bitter cold air locked in the Arctic regions of the Northern Hemisphere. It's not a single storm. On occasion, this vortex can become distorted and dip much farther south than you would normally find it, allowing cold air to spill southward.

How often does this polar vortex distortion occur?

The upper-level winds that make up the polar vortex change in intensity from time to time. When those winds decrease significantly, it can allow the vortex to become distorted, and the result is a jet stream that plunges deep into southern latitudes, bringing the cold, dense Arctic air spilling down with it.

This oscillation is known as the Arctic Oscillation and it can switch from a positive phase to negative phase a few times per year. This oscillation -- namely the negative phase where the polar winds are weaker -- tends to lead to major cold air outbreaks in one or more regions of the planet.

Where on Earth can this happen?

The polar vortex can lead to major cold air outbreaks in any portion of the Northern Hemisphere -- North America, Europe and Asia.

How dangerous is a polar vortex distortion as compared to a tornado or hurricane?

They are completely different types of systems. A cold air outbreak caused by the polar vortex is much more widespread and lasts longer than a single storm. With the widespread drop in temperature, however, you can see significant winter storms develop, especially when the cold air is initially advancing into a previously warm region -- much like the nor'easter during the past week.

When did the last one hit a densely populated area?

Serious cold snaps happen several times a year, though in different regions of the world and with different degrees of severity. Most notable was the polar vortex in the winter of 2014 when cold arctic air spilled out across North America.

It was the first year that the phrase polar vortex was used extensively in the mainstream media. The term took off, especially on Twitter, and meteorologists have been trying to clarify what the name means.

If you get caught up in one, what should you do?

Again, it's not a 'storm' that you get caught in. But when faced with significant cold temperatures, you should stay inside whenever possible, layer clothing if you must be outside, winterize your home and car, etc.

Is it a side effect of global warming and should we expect more events like this?

This is a hotly researched topic. In short, yes, it could be. It seems counterintuitive that global warming could cause significant cold snaps like this one, but some research shows that it could.

We know that different types of extreme weather can result from the overall warming of the planet, melting of the Arctic Sea ice, etc.

This includes extreme distortions of the jet stream, which can cause heat waves in summer and cold snaps in winter.

California Coronavirus Cases

Data is updated nightly.

Cases: 3095814

Reported Deaths: 35549
CountyCasesDeaths
Los Angeles104602114641
San Bernardino2587421561
Riverside2558082739
San Diego2197312222
Orange2178492546
Santa Clara959361158
Kern87240572
Fresno83591968
Sacramento816871128
Alameda69107842
Ventura63413462
San Joaquin58843788
Contra Costa53349460
Stanislaus43392773
Tulare42186515
Monterey36464255
San Mateo33207309
San Francisco29665274
Solano26191108
Santa Barbara25405243
Imperial25380486
Merced24570316
Sonoma24262242
Kings19588148
Placer17584186
San Luis Obispo16056140
Madera13585151
Santa Cruz12461113
Marin11732159
Yolo10852138
Shasta9750123
Butte9582128
El Dorado788649
Sutter782879
Napa773145
Lassen519916
San Benito504246
Yuba499627
Tehama433244
Tuolumne340340
Nevada323874
Mendocino319232
Amador303631
Lake264631
Humboldt245825
Glenn195520
Colusa17969
Calaveras163723
Siskiyou145713
Mono11244
Inyo98329
Del Norte8672
Plumas5895
Modoc3853
Mariposa3464
Trinity3044
Sierra820
Alpine730
Unassigned00
Chico
Cloudy
46° wxIcon
Hi: 50° Lo: 46°
Feels Like: 43°
Oroville
Cloudy
52° wxIcon
Hi: 50° Lo: 44°
Feels Like: 52°
Chico
Cloudy
46° wxIcon
Hi: 44° Lo: 37°
Feels Like: 43°
Red Bluff
Cloudy
51° wxIcon
Hi: 32° Lo: 26°
Feels Like: 51°
Red Bluff
Mostly Cloudy
51° wxIcon
Hi: 51° Lo: 38°
Feels Like: 51°
Chico
Partly Cloudy
46° wxIcon
Hi: 54° Lo: 39°
Feels Like: 43°
Light rain and snow is expected in your Friday forecast. We'll be mostly dry and warmer on Saturday. A more substantial system with lower snow levels is in your forecast for Sunday into early Monday. Long range models are showing very wet weather for the middle of next week.
KHSL Severe
KHSL Radar
KHSL Temperatures

Community Events