Brrrrr! Autumn's chill is creeping in across much of Europe, hinting at the deep freeze to come this winter.

Fortunately, Gas Infrastructure Europe, the gas operators' association, reports that European Union gas reserves are at just over 80% [September 15, 2025] -- lower than the 90% cushions of the last few years but stronger than 2021. So will this winter glow with warmth or flicker with uncertainty?

Having diversified energy supplies from Russia following Moscow's full-scale invasion of Ukraine in 2022, EU countries pivoted to liquified natural gas (LNG) from Norway, the United States and Qatar, while continuing to boost the rollout of renewable energies, including solar and wind.

Over the past two years, thanks to that extra capacity, Europe was able to ensure its gas reserves were almost full by September, providing an additional cushion for the coldest months of the year. Gas stocks should remain robust this winter, too.

With the EU no longer in an acute energy crisis, Brussels is being flexible in giving EU gas stocks an extra month, till December 1, to reach 90% capacity, if required. Europe also used up more of its gas reserves last winter, leaving less of a surplus than usual.

Petras Katinas, energy analyst at the Center for Research on Energy and Clean Air, says current storage levels and alternative supplies provide a "solid buffer" against supply disruptions. "But rapid withdrawals and weather volatility could still cause temporary price spikes or localized shortages," he told DW.

Complementing Europe's internal resilience, global supply conditions and stable prices are also supporting the bloc's energy preparedness for winter.

According to Tom Marzec-Manzer, from the global research and consultancy house Wood Mackenzie, global energy supply is up this year, while demand -- especially for gas -- is likely weaker.

"That has been a real benefit to refilling Europe's storage units this summer, which are continuing at a nice clip," the consultancy's Director Europe Gas & LNG told DW.

Despite this, the bloc remains vulnerable to geopolitical shocks, not least those stemming from US President Donald Trump's tariffs.

Trump is pressuring Brussels to put sanctions on buyers of Russian energy, arguing that it will pile additional financial strain on Moscow to end the three-and-a-half-year conflict.

Last week, US Treasury Secretary Scott Bessent told the EU and the Group of 7 (G7) wealthy nations that they should join Washington in imposing "meaningful" tariffs on China and India over their energy deals with Moscow.

Trump has told Brussels that the US would "mirror" such tariffs, with a rate of 100% being considered.

Trump has already imposed 50% tariffs on India -- 25% baseline plus 25% for striking a deal with Moscow in 2022 to buy discounted hydrocarbons.

However, China -- which has also ramped up purchases of Russian energy -- holds a significantly stronger negotiating position with Washington over Trump's tariff threat. As a result, the US president has yet to outline plans for energy-related tariffs on the world's second-largest economy, while negotiations remain ongoing.

The expiration of the Ukraine-Russia gas transit agreement on January 1 marked another layer of geopolitical pressure on Europe's energy supply. Kyiv's decision not to renew the deal was also aimed at cutting off a revenue stream that helps fund Russia's war effort.

The five-year agreement, which had allowed Russian gas to flow westward via Ukrainian pipelines, effectively closed one of the last major routes into the EU.

Initial fears of price spikes and supply disruptions were widespread, particularly in countries like Austria, Slovakia and Hungary, which had remained more reliant on Russian pipeline gas. Benchmark gas prices rose nearly 50% at points last year amid concerns about cold weather and reduced flows.

Yet the actual market impact was muted. Western Europe had already diversified its energy sources, while underground storage levels remained strong heading into winter.

"The drop-off in volumes [via Ukraine] hasn't been huge, although some countries, particularly Slovakia, had to reorient some purchases," Tom Marzec-Manzer said. "Because it was well-anticipated, the end of the Ukraine gas transit deal didn't have a huge price or supply impact."

Having ridden the energy crisis, the EU is now in a stronger position to diversify the last of its supplies of Russian hydrocarbons. The bloc has already cut Russian gas imports from 45% to 19%, while Russian oil imports have shrunk from 27% at the start of the war to just 3% last year, according to the European Commission, the bloc's executive arm.

In May, the Commission published a detailed roadmap to completely ban all remaining imports of Russian gas and liquefied natural gas by 2027. The plan requires EU states to submit national plans for the phaseout of Russian gas by the end of the year, but this could still prove tricky for some.

"The Baltics have done an excellent job moving away from Russian fossil fuels, while Poland has largely phased out Russian gas," Katinas told DW. He said progress has been "uneven" in other Visegrad countries due to a lack of diversification efforts and investment in renewables.

The EU's strong gas stocks and varied supply lines are bolstering the bloc's winter readiness, yet Trump's tariff moves and unpredictable weather cloud the horizon. Natural gas prices won't likely climb to 2022's nearly €340/MWh ($400) extremes, but isolated shortages could spark temporary spikes.

Is Europe prepared for winter despite lower gas supplies?