According to the national weather service, temperatures are expected to fall to between minus 20°C and minus 30°C in most regions.
Only the south-west and the far western edges of the country are expected to avoid the worst of the cold.
The deputy interior minister, Wiesław Szczepański, said the night from Sunday to Monday would be among the coldest in recent weeks.
Speaking after an emergency briefing with services at the Government Security Centre, he warned that conditions could be particularly harsh in the east of the country.
"In Suwałki, temperatures could drop to minus 29°C tonight, while the felt temperature may reach between minus 36°C and minus 38°C," he said.
Szczepański added that the cold air mass would mainly affect eastern Poland, including northern and eastern Mazowieckie and the Lubelskie region, and also parts of Pomorskie.
As a precaution, some schools in the Mazowieckie, Pomorskie and Warmińsko-Mazurskie regions have cancelled lessons.
Szczepański said at least 38 people had died from hypothermia so far this winter.
One person died from the cold in the past 24 hours alone, bringing this season’s toll to more than double the 16 deaths recorded during the same period last year.
Authorities are still awaiting post-mortem results in two further cases, which could raise the number to 40.
A further 54 people have died this winter from carbon monoxide poisoning.
Emergency services, including around 8,600 police officers, are searching abandoned buildings, bin shelters and manholes for people seeking refuge from the cold.
Special tents have been set up, and railway stations are being left open overnight to provide shelter.
In Olsztyn, north-eastern Poland, 20 homeless people spent the night at the main station.
(ał)
Source: IAR, PAP