NEW YORK — When computer coders at the IntercontinentalExchange built a platform for trading natural gas in 2001, they only allowed space for two-digit entries. With gas around $5 per million British thermal units, prices above $99 just didn’t seem feasible.

A freezing start to 2014 changed all that.

After prices in the poorly supplied Northeast spiked to new highs in the first week of January, ICE raised the limit for trades from $99 to $199 per million British thermal units on Jan. 6, reflecting a new reality in the U.S. gas market and ushering in a three-digit era.

It was a prescient move. In a second bout of cold on Tuesday, next-day gas prices in New York City broke $100 for the first time ever, and then some. Prices on the Transco pipeline at the New York Citygate surged as high as $135 per mmBtu as snow fell across the city, and forecasters predicted another cold spell.

On average, gas on the Transco line in New York sold for $120 on Tuesday, breaking the $55 record set on Jan. 6.

Atlanta-based ICE, which runs financial exchanges, confirmed the change to pricing limits but declined to give a reason.

The United States has ample supplies of gas, but the price spikes reflect a recurring conundrum: A lack of pipelines to take gas from major supply centers to market. This bottleneck pushes prices higher during periods of high demand like the first few weeks of this year.

Tuesday’s rise in prices was an example of “scarcity pricing” caused by weaknesses in the U.S. natural gas delivery system to the Northeast, said Teri Viswanath, an analyst at BNP Paribas.

“There is a growing problem with our infrastructure, and the events this week highlight the known problem with insufficient pipeline capacity to meet the growing demand for gas in the Northeast region,” said Viswanath.

At any price

Likely purchasers of Tuesday’s $100-plus gas were gas-fired power plants ordered by New York’s power grid operator to supply power on Wednesday, regardless of the price.

Some plants that do not have the option of burning other fuels were picked to keep heat flowing, a spokesman for New York Independent System Operator, which coordinates power supply to the state, told Reuters on Tuesday, on a day when temperatures did not breach 13 degrees Fahrenheit.

Plants caught empty-handed had to pay whatever price would persuade suppliers with extra inventory to sell. Sometimes, businesses with firm supply are willing to shut down for the day and sell their gas — at a steep premium.

“The price has to move up to a level that attracts some of that extra inventory into the marketplace,” said Tim Evans, an energy analyst at market research unit Citi Futures Perspective.

Prices could rise even further as gas takes the place of coal as a cleaner alternative for power generation in the coming years. Many coal plants are slated to retire in the Northeast, limiting the amount of coal that can be used generate power when gas prices go too high.

Power generators caught short of supply will feel the pinch by a fuel commonly thought to be booming in production.

“It’s dangerous to the financial health of lots of people, especially consumers who didn’t book up a fixed-price contract for the full winter,” Evans said.