Finland recently had 22 days of temperatures over 30C, the longest such heatwave since records began in 1961, the Finnish Meteorological Institute said Monday.

In the arctic town of Rovaniemi, which bills itself the hometown of Santa Claus, temperatures hit 26C on Tuesday.

Anne Ollila, director of the country's Reindeer Herders' Association, said that while the animals can cope well in freezing temperatures, heat is "a different story".

"We have had a very long and harsh heatwave period here in Lapland, and the reindeer have suffered greatly as a result," she said.

Fleeing from predators such as wolves, for example, is particularly taxing for reindeer in the heat, she said.

"They are unable to regulate their body temperature sufficiently and overheat," Ollila said.

"Not all reindeer have survived the heatwave, but there have been no reports of mass deaths."

Typically roaming in forests during the summer, many of the animals are instead seeking shade and escaping horseflies and mosquitos near settlements, at times in people's backyards.

Compared to other parts of the planet, the Arctic region is heating more rapidly due to climate change.

Of the continents overall, Europe has seen the fastest warming per decade since 1990, followed closely by Asia, according to the US National Oceanic and Atmospheric Administration (NOAA).

Scientists say recurring heatwaves are a marker of global warming and are expected to become more frequent, longer and more intense.