The current cold front that has claimed hundreds of lives in eastern Europe is making its way west.
The Kvilda region of the Czech Republic saw the mercury plunge to minus 39.4 degrees Celsius (-38.9 F).
Carbon monoxide poisoning from faulty gas heaters or in fires is also contributing to the deaths.
Helicopters ferried food and medicine to iced-in villagers Wednesday as Europe's 12-day-old cold snap tightened its frigid grip on the continent, where more than 400 have died as a result.
More than 70,000 people remained cut off from the outside world in Serbia and other Balkan countries. In southern Croatia more than 100 villages were isolated for the sixth consecutive day.
In Serbia, ice-breakers on Tuesday were summoned from Hungary in an attempt to keep the Danube flowing, while army demolition experts sought to dynamite ice barriers that threatened to provoke flooding on tributary rivers, including the Ibar.
The Danube, one of Europe's main rivers and a crucial transportation hub for eastern Europe, was barely navigable around Belgrade, and the port authority in Veliko Gradiste, near the Romanian and Bulgarian border, said river traffic was blocked along a 170-kilometre (105-mile) long stretch, from Kostolac to the Djerdap I hydropower plant.
"I have some 30 vessels blocked in Veliko Gradiste," an official said.
Other countries linked by the Danube, including Austria, Bulgaria and Romania, also threw their forces into the battle as temperatures remained well below freezing.
In Bulgaria the Danube exploration agency said icing was at 20 percent near the Serbian border and up to 80 percent along a 220-kilometer stretch between the ports of Nikopol and Silistra further down river.
Navigation was impossible, the agency said, adding that the Danube delta leading into the Black Sea in Romania was completely frozen. All traffic has been suspended since Tuesday and the main border crossing with Romania closed due to ice.
Upstream in Hungary, 13 icebreakers went into action but only managed to clear the ports of Baja and Gyor.
Ships were still moving in the area, but the ice was slowing traffic considerably, Hungary said.
"If the temperatures continue to be this low the ice could solidify on the Danube during next week as is already the case for smaller rivers," Istvan Land, director of Hungary's government water and environment agency OMIT.
In Austria, several river locks on the Danube were closed and river traffic was interrupted between southern Germany and parts of upper Austria.
Authorities said two more people had died from the cold in the rugged mountainous Balkan nation, raising the toll to seven, while Albania reported its first victim, a man aged 37 found dead near Tirana.
Bosnian authorities sent civilian and military helicopters to isolated hamlets near Mostar and Kalinovic on Wednesday, bringing much-needed supplies like flour and oil, and ferrying sick people to hospitals.
Heavy snows eased in Bosnia but the bitter cold continued, especially in the south and southeast where temperatures dropped to minus 20 degrees Celsius (minus 4 Fahrenheit.)
Thousands struggled without power, including around the historic city of Mostar, where some 15,000 homes had no electricity.
Schools were shut in large parts of Romania, including Bucharest, while many train services were canceled. Around 40 percent of roads were also closed, although flights did resume from Bucharest airport.
Miserable conditions persisted in Bulgaria. Four more people were found dead under snow in the Pernik region in the country's west, raising the death toll to 20 as authorities declared a national day of mourning for eight people drowned Monday after rivers flooded and a burst dam sent freezing waters into the village of Biser. Two residents are still missing.
Russian authorities said at least 110 people had died as a result of the cold so far this year, 44 of them in the first week of February alone.
"Weather like this (comes) only once in five years, it's usually much warmer," said Moscow resident Pavel Sterlikov.
Ukraine remained the worst-affected country, with hundreds of cars stranded on the Crimean peninsula and at least 131 deaths so far, while three more people froze to death in Romania, bringing that country's total to 41.
The coldest place Tuesday night was the Kvilda region of the Czech Republic where the mercury plunged to minus 39.4 degrees Celsius (-38.9 Fahrenheit).
The numbers killed by hypothermia in Poland has risen to 68.
The cold snap has also seen a sharp rise in the number of people being killed by carbon monoxide poisoning from faulty gas heaters or in fires, with 50 such cases in Poland alone.
The UN weather service said temperatures would remain low until March.
"We might expect the change in the current cold wave to to start easing from the start of next week up to the end of the month," Omar Baddour, a scientist at the World Meteorological Organization, told reporters.
It was a similar message from Britain where forecasters said the cold spell could last for two more weeks and heavy snow at the weekend.
In Germany, the cold allowed professional ice hockey team the Hamburg Freezers to hold their first-ever training session on the frozen Alster river amid reports of grave-diggers having to use pneumatic drills to break frozen ground and even penguins hiding indoors at a west German zoo.
The country, which decided last year to abandon nuclear power, was forced to bring several reactors back on line to deal with the peak in electricity demand, the daily Handelsblatt reported.