Tallinn has a humid continental climate. It means Tallinn enjoys warm summers and cold winters. The coastal location of Tallinn means that the winters are milder than other cities that lie on the same latitude.
The winters often see heavy snowfall that stays on the ground with February being the coldest month of the year. The average temperature in February is -4 ºC. In January and December, the temperatures are slightly warmer with temperatures averaging around 0 ºC.
The spring and autumn are mild with rainfall. But March and November both experience temperatures around freezing as seasonal lows close to winter.
The summer experiences average temperatures of between 19 ºC and 21 ºC during the day. The night can drop to between 9 ºC and 12 ºC.
Source: World Weather Online