Temperatures plummeted to frigid lows this week as the polar vortex drifted across the Midwest. In Chicago, temperatures fell to minus 23 degrees Fahrenheit, coming close to the all-time record of -27°.

The cold has also been deadly; it’s been blamed for at least nine deaths this week.

Yet amid the icy blast, some people were told to turn down the heat. In Minnesota, Xcel Energy asked more than 400,000 of its customers to leave their thermostats at 63° through Thursday. In Michigan, Consumers Energy asked its customers to turn the heat down to 65° until Friday.

Due to extremely high demand for natural gas with record-low temperatures, and an incident at a facility, @ConsumersEnergy has asked everyone who is able to please turn down their thermostats to 65° or less until Friday at noon. #MIREADY pic.twitter.com/FWKCZnu9QA — Governor Gretchen Whitmer (@gretchenwhitmer) January 31, 2019

Why? Demand for natural gas is likely to hit a record high this week, and the heating fuel is in short supply in the region.

While electricity production can ramp up and down to match demand, natural gas production is much more complicated, so it’s harder to cope with a sudden spike in usage. There are options to store natural gas underground to deal with such scenarios, but at the same time, the cold is leading to freeze-offs (when water and other liquids in natural gas pipelines freeze, obstructing the flow of gas). Freeze-offs can drastically limit the amount of natural gas available, comparable to the impacts of hurricanes on natural gas infrastructure.

For Michigan, another major factor in the gas shortage was a fire at a Consumers Energy gas compressor facility on Wednesday.

So with this high demand and lower supply, utilities are worried there may not be enough gas to go around for everyone to keep their homes toasty. Hence, the requests to leave thermostats in the low to mid-60s.

To all Michiganders: We truly thank you for your help and patience during this time of need. pic.twitter.com/jmNvm2zTnI — Consumers Energy (@ConsumersEnergy) January 31, 2019

And actually, asking customers to turn down the heat is a tactic that the energy industry wants to use more and more. The term for this is “demand response.” Utilities are already testing this with electricity, pricing power in real time to encourage customers to run dishwashers and air conditioners in off-peak hours when electricity is cheap and abundant.

In 2018, the New York Public Service Commission approved a pilot program from Consolidated Edison to test demand response for natural gas. One method will essentially allow the utility to control the thermostat in a home on peak gas demand days in exchange for a rebate or other financial incentive for the customer. The goal is to shave off some of the peak gas demand, thereby reducing the need for new pipelines and natural contracts for the utility.

The White House, meanwhile, has raised the specter of natural gas supply shortages like this one as a national security issue, invoking it as a justification for building new natural gas pipelines.

For those in Michigan, please listen to your State and local authorities tonight and tomorrow re natural gas use in the coming days. https://t.co/7n8fdf9OtE — NSC (@WHNSC) January 31, 2019

More broadly, the recent severe cold reveals yet another vulnerability in energy infrastructure. Utilities and public officials readily brace for storms and heat but can get caught off guard when temperatures drop. We’ve already seen thousands of people lose power in Wisconsin this week as hardware like insulators and fuses became brittle and failed in the cold. Blackouts in Minnesota were also blamed on low temperatures as the cold caused wires to contract and utility poles fractured. A string of cold-related power outages struck Illinois as well. So demand response, for both electricity and gas, may become a larger part of coping with the cold in the future.