HELSINKI - A heatwave sweeping across Europe has pushed temperatures above 20 degrees Celsius in Finland and Sweden, with some areas exceeding 30 degrees, prompting health and safety warnings.

As of early Monday evening, the Finnish Meteorological Institute (FMI) issued yellow-level alerts for "potentially dangerous temperatures" across most of Finland. Sweden issued similar warnings, particularly in the north.

Heat alert thresholds differ by country. In Finland, warnings are triggered when highs reach 27 degrees or daily averages exceed 20 degrees. In Sweden, yellow alerts are issued if temperatures are forecast to exceed 30 degrees for four consecutive days.

On Monday, Finland experienced widespread hot and sunny weather, with temperatures exceeding 30 degrees in many areas including the capital region, according to the FMI.

The heat follows a cooler, wetter start to summer. A national high of 31.5 degrees this summer, recorded Sunday in southwestern Finland's Kaskinen, was surpassed on Monday, when the FMI reported 31.6 degrees -- again in the city.

"This week is shaping up to be the hottest of the summer so far," FMI meteorologist Jani Sorsa told Finnish News Agency STT on Monday.

In response to the heat, Finland's Institute for Health and Welfare (THL) issued health warnings urging people -- especially those over 75 -- to stay hydrated, avoid direct sunlight, and reduce physical exertion.

Swedish Meteorological and Hydrological Institute (SMHI) forecast highs of 26-33 degrees in parts of the country, warning residents to watch for signs of overheating and dehydration in themselves and others.

Swedish Television meteorologist Nils Holmqvist warned that up to 600 heat-related deaths could occur under the current conditions.

In Finland, THL specialist Virpi Kollanus said heat-related deaths have risen since 2000, reversing a downward trend seen since the 1970s. "The earlier decline likely resulted from better living standards and improved public health," she told broadcaster Yle. "Now, heatwaves are more frequent and the population is aging."

The FMI noted that prolonged heat remains rare in Finland. Two-week heatwaves occur roughly once a decade. Since 1961, six three-week periods have been recorded, most recently in 2021.