Temperatures in Verkhoyansk, a remote Siberian town in the Arctic Circle, hit 38 deg C last Saturday, about 18 deg C above the average maximum daily reading in June. If confirmed, it would be the Arctic's hottest temperature on record, the BBC and other media reported.
It fits a pattern. Scientists say the Arctic is warming at more than twice the rate of the rest of the globe and the region has been regularly breaking temperature records.
The hot weather follows weeks of abnormally high temperatures in far northern Russia, helping fuel huge wildfires in Siberia that are likely to burn for months.
It also comes as 2020 shapes up to be one of the hottest years ever. Last month was tied with May 2016 as the hottest May on record, while the months of January to April were either the hottest or second hottest.
Nineteen of the 20 warmest years have all occurred since 2001, with the exception of 1998.
The year 2016 ranks as the warmest on record, according to the US space agency National Aeronautics and Space Administration.
Verkhoyansk, home to about 1,300 people, is just inside the Arctic Circle. It has an extreme climate with temperatures plunging in January to an average maximum of minus 42 deg C and then surging in June to 20 deg C, noted the BBC.
A persistent heatwave this year in the Arctic Circle has worried meteorologists. In March, April and May, the European Commission's Copernicus Climate Change Service (C3S) said the average temperature was about 10 deg C above normal.
Dr Freja Vamborg, a senior climate scientist at C3S, said in a commentary last week: "It is undoubtedly an alarming sign. The whole of winter and spring had repeated periods of higher-than-average surface air temperatures."
She noted that while the planet as a whole is warming, it is not even: "Western Siberia... shows more of a warming trend with higher variations in temperature."
Dr Vamborg added: "However, what is unusual is how long the warmer-than-average anomalies have persisted."
Scientists say the northern and parts of the southern polar regions are heating much faster, with growing amounts of greenhouse gases - chiefly carbon dioxide (CO2) - from burning fossil fuels, forest fires and agriculture heating up the planet.
The extreme temperatures in Siberia and elsewhere in the Arctic are particularly worrying for scientists for a number of reasons.
The Arctic has a thick layer of permanently frozen soil under the surface that is now melting. That ice layer has large amounts of methane, an even more powerful greenhouse gas than CO2, and more methane in the atmosphere could accelerate climate change.
Ice on land and on sea also helps keep the planet cool by reflecting the sun's energy. As more of it melts, more of the sun's energy is absorbed by the oceans and land.
The Arctic also has, in its huge forests, one of the largest stores of carbon on the planet. Higher temperatures in the Arctic are creating conditions for larger and more intense fires that are releasing large amounts of CO2.
In recent days, the number and intensity of wildfires in north-east Siberia and the Arctic Circle have continued to increase, according to an analysis by the Copernicus Atmosphere Monitoring Service.
The daily total intensity is at similar levels to last year's, Dr Mark Parrington, from the European Centre for Medium-Range Weather Forecasts, said on Twitter.
Last year, wildfires in Siberia burned for months, sweeping through millions of hectares. Those fires were followed by huge forest fires in South America and record bush fires in eastern Australia.