Natural gas surged above $9 per million British thermal units, or MMBtu, on Wednesday, hitting the highest level in more than a decade as dwindling inventories push prices higher.

U.S. prices surged more than 6% at one point to hit a high of $9.399 per MMBtu, the highest since August 2008. The contract later gave back the bulk of those gains, ending the day 1.99% higher at $8.971 per MMBtu.

Still, prices remain elevated in what's been a blistering rally for natural gas as Russia's war on Ukraine sends energy markets reeling.

David Givens, head of natural gas and power services for North America at Argus Media, pointed to three key catalysts fueling the rally: little production growth, high liquified natural gas exports, and storage levels that are roughly 17% below the five-year average.

Rapidly rising prices are adding to inflationary pressures across the economy. Drivers are already grappling with record high prices at the gas pump, and now utility bills are set to increase too. While utility companies might have once switched to coal as a cheaper alternative, coal-fueled power is also now in short supply with a number of plants going offline due in part to ESG — environmental, social and governance — concerns.

Campbell Faulkner, senior vice president and chief data analyst at OTC Global Holdings, said the drought in the Western U.S. has curtailed hydropower production.

"[G]as is being forced to fulfill a significantly greater portion of power burn during a summer that looks to top records for electricity load," he said.

"Gas for many years was the waste by-product of continued shale drilling across producing basins in the U.S. which kept prices unusually low. Since the 2020 low in drilling, the market has been pushed into a tight supply demand situation which will not be remedied quickly," he added.

Natural gas is now up nearly 30% in May, the third straight month when gains have topped 20%, and prices are now up around 150% for 2022.

Some of Wednesday's trading action could also be thanks to the futures contract's expiration on Thursday.

"Trader positioning around today's June contract options expiration and tomorrow's final settlement is likely to dominate immediate-term trading, particularly later in the session," EBW Analytics said in a note to clients.

"With ill-defined technical resistance to the high side, the potential for fireworks carrying NYMEX natural gas futures steeply higher over the next two days remains," the firm added.

Still, the more actively traded contract for July delivery also sat above $9 on Wednesday.

The S&P energy sector gained more than 1% on Wednesday and is hovering around the highest level since November 2014.