Climate

Estonia is located in the northwestern part of the East-European Plain, i.e. within a transition zone from maritime to continental climate. The main factor influencing the climate of Estonia is the Atlantic Ocean (in particular the North-Atlantic Stream), which influences the climate in the whole of Europe. The active cyclonic activity occurring in the northern part of the Atlantic Ocean (the Icelandic minimum) determines a very high variability of the weather in Estonia and causes strong winds, high precipitation and abrupt fluctuations in temperature. The latter are at their maximum in autumn and in winter. The prevailing western winds carry humid maritime air deep into the inland parts of the continent. In the cold season this brings about a considerably warmer, while in the warm season a somewhat cooler weather. The annual average temperature in Estonia is considerably higher than in more eastern areas lying on the same latitudes but having a more continental climate.

Estonia's high latitude leads to a big difference between daylight conditions in summer and in winter. Days are at their shortest on the winter solstice: in Tallinn, North Estonia, 6 hours and 2 minutes and in Valga, South Estonia, 6 hours and 39 minutes. The longest day, the summer solstice, lasts for 18 hours 40 minutes and 18 hours 10 minutes in the north and south, respectively. The annual amount of sunshine hours varies between 1600 and 1900, being higher on the coast and on the islands, and lower on the uplands. This amounts to less than half the maximum possible duration of sunshine.

Temperate maritime and continental air masses dominate in Estonia, with each occurring at a more or less equal rate. Continental air masses are more frequent in the second half of winter, in spring, and in the first half of summer. Invasions of dry and cold arctic air masses occur from time to time in winter and in spring. In exceptional cases, southern cyclones carry warm tropical air masses far up to the north in summer.

The main factor shaping the differences in air temperatures between different regions in Estonia is the Baltic Sea. In winter it keeps the coastal areas much warmer than the inland. At this time, the isotherms run from the north down to the south, during this period it is warmer in the west and colder in the east. The average air temperature in January is –6º to –7ºC in Central and East Estonia and –2º to –4ºC in the West-Estonian Archipelago. The coldest month is February.

In spring the inland warms up much faster than the sea. Therefore, coastal areas remain comparatively cooler than the rest of Estonia. Differences between the average temperatures in May exceed 3.5ºC. In summer these territorial differences begin to disappear. The average temperature in July varies between 16.0ºC and 17.4ºC. The coolest areas are located on the uplands, the warmest on the coasts of shallow inland seas, such as Pärnu Bay. In autumn, again, the inland cools down much faster than the coastal areas. Towards the winter, the contrasts in air temperatures become increasingly distinct.

The annual average temperature in Estonia is between 4.3ºC and 6.5ºC, being lower on the uplands and higher on the western coast of the islands. The highest air temperature, 35.6ºC, was measured on 11 August 1992 in Võru, the lowest, –43.5ºC, on 17 January 1940 in Jõgeva. The vegetation period lasts for 180–195 days and the frost-free period 110–190 days. Both are longer on the coast.

The annual average wind speed in the inland parts of Estonia is less than 4 m/s; on the coasts of the open seas it is more than 6 m/s. Bigger still are the differences in the frequency of storm winds. In the inland, storm winds (more than 15 m/s) are rare, occurring only a few times a year, while on the coast and islands of the open seas the frequency of storm winds reaches 30–45 days/year.

Estonia is located in a region of humid climate, where the amount of precipitation exceeds the total evaporation. The annual average of the relative air humidity is 80–83%. It is higher in winter and at its lowest in May, being 70% on average. The annual average precipitation varies between 550 and 800 mm. As a rule, the coastal zone receives less rainfall than the inland areas. It is particularly dry on the coast in spring and in the first half of summer. Areas with the highest precipitation are located on the uplands and at a distance of 30–60 km from the western coast. The latter zone receives a comparatively large amount of precipitation in autumn and early winter. The maximum recorded annual total amount of precipitation has been 1157 mm, with a maximum monthly amount of 351 mm, and a maximum twenty-four-hour amount of 148 mm.

The snow cover in Estonia is characterised by large territorial and temporal variations. The average duration of snow cover during winter is 75–135 days. Snow cover remains for the shortest time on the small islands near the western coast of Saaremaa Island and for the longest time on the Haanja and Pandivere Uplands.

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