Water temperature 1.9.2023

Surface waters have cooled down slightly but remain warmer than the average of the season

During the past week, the temperature of surface waters decreased by a few degrees, but September begins warmer than average in terms of surface waters.  Surface water temperatures were in many places 1–3 degrees Celsius warmer than the average of the season. On Thursday 31 August, the surface water temperature in southern and central Finland varied between 16 and 19 degrees. In North Ostrobothnia, the surface water temperature varied between 15 and 17 degrees and in Lapland between 13 and 16 degrees.  The warmest surface water was still at the observation site of Lauritsala in Lake Saimaa, nearly 19 degrees. According to current medium-term water system forecasts, the temperature of surface waters will gradually cool down as the autumn arrives. Surface water temperature is measured at 8 in the morning at the depth of 20 cm.


The information on this page was produced by the Finnish Environment Institute (Syke).


Nuori iloinen poika ui järvessä.

How is surface temperature of water measured?

The surface temperature of water varies significantly depending on the season and weather. Temperatures are measured daily in lakes, rivers and the sea during the ice-free season, and the results are available without delay.

Lakes and rivers

The surface water temperatures of lakes and rivers are measured at 34 monitoring stations, and temperature data are available from 80 sites in total. The measurements come from automated instruments placed at the depth of 20 centimetres close to the shore, and the results are available in almost real time. The official reference value is the reading recorded every day at 8:00 a.m.

Marine areas

At sea, surface water temperatures are measured from a depth of 20 to 30 centimetres using buoys. Water temperature data are also obtained from sea water level monitoring stations which operate round the year. Their measurements are taken at a depth of two to three metres, however, and the results cannot be compared to the readings from the buoys.

Fun facts about water temperature