 The city has a Mild Summer Continental or Hemiboreal climate ( Dfb ) according to the Köppen climate classification system , characterized by warm temperatures during summer and long and frosty winters . It is substantially different from most of the other Polish lowlands . The region is one of the coldest in Poland , with the average temperature in January being − 2 @.@ 5 ° C ( 27 ° F ) . The average temperature in a year is about 7 ° C ( 45 ° F ) . The number of frost days ranges from 50 to 60 , with frost from 110 to 138 days and the duration of snow cover from 90 to 110 days . Mean annual rainfall values oscillate around 580 mm ( 22 @.@ 8 in ) , and the vegetation period lasts 200 to 210 days . 
