United States: Schools in Chicago, Boston and other large cities closed on Thursday as sub-zero temperatures and bitter winds gripped central and eastern United States for a third day and meteorologists warned there was little relief in sight.

An Arctic air blast from Canada hit the U.S. Midwest, Mid-Atlantic and Northeast, with many parts around minus 10 Fahrenheit (minus 23 Celsius), the National Weather Service said.

In northern New York state's Adirondack Park, the village of Saranac Lake dropped to minus 24F overnight.

"While it looks like the high pressure responsible for the cold will last another day or two and then move to the east, another shot of cold air will be coming into the north-central states toward the weekend," National Weather Service meteorologist Chris Broyles said.

The service said frostbite could set in with just 15 minutes' exposure to the frigid air and advised people to keep pets indoors. Driving could be treacherous in areas hit with blowing snow and icy roadways, it added.

Chicago Public Schools, the third-largest U.S. school district with 400,000 students and almost 800 institutions, told students to stay home and indoors as temperatures dropped to between 20F and 30F below average.

Schools were also closed in Boston, Milwaukee, and Indianapolis.

Sledding hills and cross-country ski areas were shut down around Chicago. In South Dakota, the city of Sioux Falls closed six ice-skating rinks, saying there was a risk of wind chill.

The weather service issued wind chill alerts for Chicago, Minneapolis, and other cities. Overnight wind chill values in most areas reached minus 15F to minus 25F.

The weather service said blizzard conditions were forecast for parts of North Dakota and Minnesota through the afternoon on Thursday. In South Dakota, blowing snow and low viability would continue through the day.

"It makes the conditions extremely hazardous to travel," Broyles said.

Temperatures also plummeted to an uncharacteristic 10F to 15F across the Gulf Coast overnight, where a hard freeze warning was issued for east Texas across parts of Louisiana, Mississippi and southern Georgia, Broyles said.