Frigid air is blowing across the United States, dropping temperatures in many areas into the single digits and leading weather monitors to issue wind chill advisories and politicians to plead with residents to check on their neighbors.

A National Weather Service wind chill advisory for much of the Northeast for Wednesday into Thursday warns of “dangerously cold air” with strong winds that could result in frostbite if people don’t put on their scarves, hats and gloves.

Here’s a look at how the winter weather plaguing almost two-thirds of the country is playing out and what’s to come.

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OPENINGS AND CLOSINGS

A stretch of the Thruway in western New York reopened after being shut down in both directions for more than three hours Tuesday night into Wednesday morning because of severe lake-effect storms near Lake Erie.

A 40-mile section of Interstate 90’s eastbound lanes closed shortly before midnight Tuesday. A 50-mile stretch of the highway’s westbound lanes from closed around the same time. The Thruway reopened in both directions around 3:15 a.m. Wednesday.

Tuesday’s lake-effect storms along the eastern shore of Lake Ontario dumped about a foot of snow on areas south of Buffalo

The blast of arctic air that’s blanketing most of the country prompted schools to close or delay openings from Alabama to the Dakotas.

Wind chill advisories and warnings for North Dakota and South Dakota, with the combination of arctic air and wind pushing wind chills into the minus 20s and 30s led to dozens of schools either closing or delaying their opening. The weather service has posted blizzard watches for southeastern South Dakota and northeastern North Dakota on Thursday.

Schools pushed back their starting times across Central and north Alabama because of the bitterly cold weather. In Tennessee, some schools that closed Wednesday planned to remain shut down on Thursday.

Dozens of school districts in Illinois, including Chicago Public Schools, canceled Wednesday classes due to subzero temperatures. In Indiana, Indianapolis Public Schools, one of the state’s largest school districts, canceled Wednesday’s classes, as did many others across the state’s northern half, where a daylong wind chill warning was in effect. There were also numerous school closings in Wisconsin and Minnesota.

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NORTHEAST, BUNDLE UP!

Residents across the Northeast have been warned: It’s brutally cold and getting colder.

The National Weather Service said already cold temperatures in the region dropped to the mid-teens early Wednesday and were expected to fall to the single digits before the morning commute. It said an arctic front moving in from the north and west had a chance of producing wind gusts up to 40 mph by afternoon.

Nighttime? Even colder, with wind chills of about 15 degrees below zero in the New York metro area and 20 below farther north.

New York Mayor Bill de Blasio urged people in the nation’s largest city to prepare for temperatures expected to drop to 9 degrees on Wednesday night. He reminded them to watch over neighbors and relatives who may be at risk and asked service providers to check on their clients.

In Connecticut, officials urged people in need of shelter to call the 211 hotline as the state braced for a frigid blast. A cold-weather protocol activated by Gov. Dannel P. Malloy directs state agencies to coordinate with the hotline and the network of shelters to make sure the state’s most vulnerable residents are protected from the cold.

New Jersey is cleaning up from a snowfall that caused slick roads and numerous accidents.

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MOVE OVER, SNOW; WELCOME, COLD

Ohio residents who sighed with relief as snowfall that caused hazardous road conditions moved out of the state were warned to prepare for single-digit temperatures and wind chills below zero.

Early snowfall Tuesday led to slow morning commutes and numerous traffic accidents across the state. A Highway Patrol trooper was among four people injured when a woman lost control of her car on a slick highway in Clermont County and struck a police cruiser.

The forecast for Wednesday into Thursday calls for temperatures below zero for most of the state and wind chills possibly as low as 20 to 30 below zero.

Duke Energy said it’s prepared for increased demand but advised customers to check supplies of flashlights, batteries, bottled water and medicines. Columbia Gas of Ohio warned customers not to use ovens or ranges to heat their homes.

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… AND IN CALIFORNIA

A Central and Southern California winter heat wave has set records with highs topping 80 degrees.

Santa Maria’s airport on Tuesday recorded a maximum temperature of 82 degrees, 2 degrees above records for the day set in 1962 and 1918. Santa Barbara’s airport also hit 82 degrees, well above the 78 recorded in 1964.

Highs in the low to mid-80s set or tied records in Camarillo, in Burbank and at UCLA.

In San Diego County, Escondido’s 87 beat the 86 recorded in 1969, and Alpine topped a 1969 record with a high of 82.

The National Weather Service said the heat will continue through Wednesday but cooler conditions beginning Friday could drop some areas into the 60s over the weekend.

(AP)