Tallinn has a humid continental climate that 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 with an average temperature of -4 degrees Celsius. In January and December the temperatures are slightly warmer with temperatures averaging around 0 degrees Celsius.
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 degrees Celsius and 21 degrees Celsius during the day though temperatures during the night can drop to between 9 degrees Celsius and 12 degrees Celsius.
Source: World Weather Online