Power and natural gas prices across North America soared to their highest in years on Friday as freezing wells cut output and homes and businesses crank up their heaters to escape the arctic blast moving across Canada and the United States.

"Close to 20 million Americans throughout the country's mid-section can expect to be impacted by winter weather in the coming days," meteorologists at AccuWeather said, including a weather system that could deliver a big blast to Dallas, which hasn't recorded snow yet this season.

High temperatures in Chicago are expected to remain below freezing (32 Fahrenheit or zero Celsius) until around Feb. 20 with some of the coldest yet to come when overnight lows plunge to -3 F on Sunday, AccuWeather said. The normal high in the city at this time of year is 35 F.

That cold air will move East over the weekend and could drop snow from Arkansas to Maine early next week.

Next-day power for Friday rose to its highest since 2019 at the PJM West hub in the mid Atlantic and Ercot North in Texas.

Energy traders said some 5-minute power prices in Texas approached $4,000 per megawatt hour on Thursday. That compares with an Ercot North average of $26 in 2020.

Spot gas for Friday rose to its highest since 2014 at the Waha hub in West Texas and AECO in Alberta.

See table below for more prices.

Data provider Refinitiv said US output was on track to drop from 87.7 billion cubic feet per day (bcfd) on Thursday to 85.3 bcfd on Friday, its lowest since October.

Energy traders said wellhead freeze-offs in many regions caused that decline, including losses of around 1.6 bcfd along the Gulf Coast, 0.3 bcfd in Appalachia, 1.1 bcfd in the Midcontinent, 0.3 bcfd in the Rockies, 0.1 bcfd in New Mexico and 0.1 bcfd in North Dakota.

One billion cubic feet is enough gas to supply about five million US homes for a day.