NEW YORK: US natural gas futures fell 10% on Tuesday, reversing Monday’s gains due to a shift to a slightly warmer weather outlook after expectations of a cold snap sent prices soaring in the last session.

Front-month gas futures slipped 10% to $7.048 per million British thermal units as of 12:28 p.m. EDT (1628 GMT) after days of gains took prices to a 13-year high. Traders said the market’s long rally left prices at a level that was not sustainable based on fundamentals.

On Monday, prices soared due to an unseasonable cold snap outlook for the United States at a time when the natural gas market generally shifts to moving gas into storage in preparation for the next winter.

“The weather, of course, and overbought (price action) is bringing the market back down to earth to a more reliable pattern,” said Phil Flynn, an analyst at Price Futures Group.

This market is “still in a very strong position because inventories are below average,” Flynn added.

Data provider Refinitiv estimated 130 heating degree days (HDDs) over the next two weeks in the Lower 48 US states, slipping from Monday’s outlook of 156 HDDs, though slightly higher than the 30-year norm of 126 HDDs for this time of year.

HDDs, used to estimate demand to heat homes and businesses, measure the number of degrees a day’s average temperature is below 65 Fahrenheit (18 Celsius).

“A milder outlook for US weather will arrive in the short-term, but another cold snap could be around the corner by early May,” Isaac Hankes, senior weather research analyst at Refinitiv, said in a daily forecast note.

Meanwhile, data from Refinitiv showed average gas output in the US Lower 48 states rose to 94.5 billion cubic feet per day (bcfd) so far in April from 93.7 bcfd in March, down from December’s monthly record of 96.3 bcfd.