It´s the first time since 2010, when temperatures in lowlands in Poland dropped below -25°C! /https://tvn24.pl/tvnmeteo/informacje-pogoda/polska,28/prawie-28-stopni-mrozu-to-byla-najzimniejsza-noc-od-11-lat,333371,1,0.html?p=meteo/.
The strongest frosts for 11 years brought minimally -27,8°C, although, absolute winter minimum should be even lower (next Siberian blast is still possible https://mkweather.com/2021/01/17/a-big-comeback-of-cruel-winter-30celsius-around-1-february-2021-the-second-peak-is-confirming-2021/ and data from some stations will be collected only during next days, or at the end of the month).
IMGW informed, that within its main meteorological site, minimum temperatures dropped up to -27,8°C in Monday´s morning (Gołdapi). In Jabłonowie-Wypych was measured -26,5°C, in Suwałki -26,4°C and in Białystok -25,4°C. Tempertures near ground dropped in Bialystok up to -33°C! /https://www.tvp.info/51849510/prognoza-pogody-dlugoterminowa-zima-2021-bestia-ze-wschodu-kiedy-odejdzie-imgw-wydaje-alerty-potezny-mroz-nad-polska-minus-dwadziescia-stopni-prognoza-dlugoterminowa-tvp-info/
Some regions however, repoted frosts around -30°C according to /https://www.polsatnews.pl/wiadomosc/2021-01-18/rekordowy-mroz-na-wschodzie-polski-odwolane-zajecia-w-szkole//, e.g. Sztabin. Minimum temperatures from many stations will be known only tomorrow or at the end of the month, because from some "little" stations go reports into databases only once a day, from some only once monthly. Therefore it is still possible, that somewhere in the northeastern Poland, -30,0°C was really overcame.
Moreover, next extremely cold night is from Monday to Tuesday expected, with GFS estimates for NE Poland only cca 2°C warmer than for Monday.
Only at 12:00 on Monday, 18. January 2021, temperature in Marianowo is reaching freezing -18,7°C and it will be next day, with regional maximum temperatures below -15°C.
In Ketrzyn -24,4°C, in Lodz, -22,5°C, in Lublin -20,9°C, in Warsaw -20,6°C, in Torun -20,3°C and in Bielsko-Biala -20,2°C was measured. Maximum temperatures in Bialystok reached -15,8°C and in Suwalki -15,4°C on Sunday, 17. January 2021.
Long- term forecasts predicting an extreme Siberian cold blast since the end of December 2020 in central Europe therefore have been successful and one of the strongest coldwaves after year 2000 really have come and bothered many regions, including Poland.
Extreme frosts hit at the weekend and on Monday Estonia, Latvia, Lithuania, Belarus, Ukraine, Slovakia, Austria, Switzerland, France, Romania, Hungary, Bulgaria, Greece, Serbia or North Macedonia, what was / will be a main topic of recent Mkweather articles.
Extreme frosts in Europe are only regional anomaly associated with extreme planetary circulation since the end of December 2020, when Northern Hemisphere have reported many temperature, snowfall or air pressure records /https://mkweather.com/2021/01/14/big-extreme-frosts-summary-temperature-records-from-europe-and-northern-hemisphere-during-the-first-half-of-the-peak-of-winter-2020-21//.