European Union countries are moving to fill their gas storage facilities quickly ahead of the winter season amid an unrelenting energy crisis and fears that Russia will cut off natural gas supplies completely.

Each EU country needs to reach at least 80% filled capacity by Nov. 1.

Collectively, the Union’s storage facilities are already 74.73% full, according to the data from Gas Infrastructure Europe, but there are differences from country to country.

While Portugal’s gas storage facility is fully filled, Austria stands at 59.28% and Bulgaria at 55.25%. Ukraine, a non-EU country but with the largest gas storage capacity in Europe, stands at 25.41%.

Germany, the most vulnerable to a Russian cutoff, managed to reach a 75% gas stock target in mid-August, ahead of the Sept, 1 national deadline. The next targets are 85% by Oct. 1 and 95% by Nov. 1, going beyond the minimum legally binding EU obligations.

But even if reserves are replenished in line with government targets, Germany will struggle to have enough natural gas to get through winter if Russia cuts off supplies completely, the country’s energy regulator said this week.

EU countries also began saving gas as of Aug. 1 through a series of measures hitting citizens’ day-to-day lives. The goal is to reduce gas consumption by 15% until the end of March to prepare for a worst-case scenario.

As Cipher recently reported in this explainer column, natural gas is not equally dominant in countries’ energy mixes. This means countries are also not all equally vulnerable to a potential supply disruption.