By Joe Wallace

Natural-gas prices have surged in Europe following a plunge in the spring, offering much-needed relief to U.S. exporters.

Spot prices for gas in the Title Transfer Facility, a virtual trading hub in the Netherlands, have rallied 265% from their trough in late May, even after slipping over the past week. Prices have gone from just under $1 per million British thermal units to $3.63 in under four months, according to S&P Global Platts.

The rebound is good news for U.S. exporters such as Cheniere Energy Inc. Cheniere and other companies invested in infrastructure for shipping gas globally over the past decade, only to contend with a collapse in sales when the pandemic struck.

Producers like Pennsylvania's EQT Corp. also stand to benefit if rising foreign demand for American gas lifts prices in the U.S.

Henry Hub gas futures edged up 0.8% to $2.38 per million British thermal units Wednesday, while U.S. crude-oil prices rose 2.2% to $39.12 a barrel.

Gas prices have bounced back faster in Europe than in the U.S. and Asia, having fallen further when much of the world economy shut down this year due to Covid-19 lockdowns.

Europe plays a key role in the international gas market, though Asia is by far the biggest buyer of American gas. Gas is primarily burned to heat homes and offices in Europe, unlike in the U.S., where power generation is the main source of domestic demand. Historically, Europe has absorbed fuel that isn't needed in other regions, partly due to flexible, commercially-operated storage facilities and an electricity market that can flip from coal to gas at speed.

Europe failed to act as the gas-buyer of last resort for the first time this summer, said James Huckstepp, a gas analyst at Platts. With storage facilities filling up because of the drop in demand, buyers canceled dozens of cargoes and prices sank to levels at which exports to Europe were lossmaking.

Shipments from the U.S. stalled. That, in turn, added to the domestic surplus of gas and helped push benchmark prices in Louisiana to 25-year lows.

A combination of factors has since spurred gas prices in Europe. Demand from factories, which burn gas for heat, has revived along with the region's economy. Maintenance work at French nuclear-power stations has required more electricity to be generated by gas-fired utilities. Rising prices for carbon credits have encouraged power plants to burn gas instead of coal and lignite.

On the supply side, European and American gas producers throttled back output this year, while outages at Chevron Corp.'s Gorgon project disrupted exports from Australia. The slide in crude prices also prompted U.S. energy companies to stop drilling for oil, which produces gas as a byproduct. New pipeline capacity running through Slovakia enabled traders to shift some of the glut of gas in Western Europe into Ukraine.

Thanks to the summer surge, European prices have recovered to levels at which exporters can profit from buying gas, liquefying it, and shipping it across the Atlantic.

Exports of liquefied-natural gas to Europe have paid a slim profit margin since late August, according to Julien Hoarau, an analyst at Engie EnergyScan. He expects exports to pick up in October, once Gulf Coast export terminals are fully up-and-running after the disruption from Hurricane Laura.

"Gas prices in Europe are higher than the cost of exporting U.S. LNG," said Mr. Hoarau, referring to liquefied-natural gas. "There is an opportunity."

Longer term, prices could get another boost if Nord Stream 2, the pipeline being built to funnel Russian gas into Germany, is delayed or abandoned. Germany has signaled it is prepared to reconsider the project, which is close to completion, in light of the poisoning of Russian opposition figure Alexei Navalny. U.S. sanctions have already halted construction of the pipeline in its last stretch.

If the project were called off, Russia's Gazprom PJSC would either have to renegotiate its transit contract with Ukraine to cater for more gas or book additional capacity on a short-term basis, according to Platts. Either way, the state-owned energy company's supply costs would likely rise, potentially lifting prices for buyers in Western Europe.

"There is a large probability it will at least be postponed for at least two years or probably indefinitely," said Christoph Merkel, managing director of German consulting firm Merkel Energy. "It has implications for the gas market but it will not move the market immediately."

A Gazprom spokesperson referred questions to Nord Stream 2 AG, which manages the project and is owned by the Russian energy company. A spokesperson for Nord Stream 2 said the company doesn't comment on political discussions.

Meanwhile, American exports to both Europe and Asia are expected to rise when colder temperatures in the Northern Hemisphere lift gas demand. The seasonal increase in demand for liquefied-natural gas will be the biggest on record, analysts at Bank of America Global Research forecast.

"There's more than enough space and appetite for U.S. LNG globally," said Trevor Sikorski, head of natural-gas and carbon research at consulting firm Energy Aspects.

Write to Joe Wallace at Joe.Wallace@wsj.com