Global climate change is partly to blame for the abnormally hot and dry weather in Moscow, cloaked in a haze of smoke from wildfires, say researchers.
The UK Met Office has said there are likely to be more extreme high temperatures in the future.
Experts from the environmental group WWF Russia have also linked climate change and hot weather to raging wildfires around the Russian capital.
Meteorologists say severe conditions may linger for several more days.
The Moscow health department said earlier that the number of people dying daily in the city had reached about 700 - twice the usual number.
Jeff Knight, a climate variability scientist at the UK Met Office, attributed the situation in Moscow to a number of factors, among them greenhouse gas concentrations, which are steadily rising.
The recent El Nino, a climate pattern that occurs across the tropical Pacific Ocean and affects weather around the world, and local weather patterns in Russia may have also contributed to this summer's abnormal conditions.
"The Russian heatwave is related to a persistent pattern of circulation drawing air from the south and east (the very warm steppes)," said Dr Knight.
"Circulation anomalies tend to create warm and cool anomalies: while it has been very hot in western Russia, it has been cooler than average in adjacent parts of Siberia that lie on the other side of the high pressure system where Arctic air is being drawn southwards.
"Some long-term records have been broken - for example the highest daily temperature in Moscow. We expect more extreme high temperatures as the climate changes. This means that when weather fluctuations promote high temperatures… there is more likelihood of records being broken."
The head of the climate and energy programme at WWF Russia, Alexei Kokorin, said the abnormal temperatures soaring to up to 40C increased the likelihood of wildfires around the capital.
And though this summer in Moscow had proven harsh for people and animals alike, it was possible that temperatures would continue to rise over the years to come, he warned.
"We have to get ready to fight such fires in the future because there is a great possibility that such a summer will be repeated. This tendency won't stop in the coming 40 years or so, until the greenhouse gas emissions are reduced," he said.
"In a few decades, fires may affect the main forest regions of Russia. Of course, there are a lot less people living there, but we could lose a lot more forests.
"We can now say that the wave of abnormal phenomena that the rest of the world has been experiencing has finally reached central Russia," Dr Kokorin added.
Temperatures have been record-high for weeks and smoke from wildfires has driven airborne pollutants levels to the worst ever recorded in the capital and the Moscow region.
How peat bog fires spread
- Peat is formed from decayed vegetation in bogs, moors or swamps.
- Deliberate drainage or drought can expose peat to air.
- Peat can then be ignited by wildfires or spontaneously combust. The air flow allows the peat to continue burning.
- Once alight, the smouldering fire spreads slowly through the peat and can cause the ground above to collapse.
Besides people suffering and entire villages burnt down, Russian wildlife has been hit hard as well.
Greenpeace Russia has criticised the Russian authorities for poor handling of the catastrophe, and mainly for abolishing a centralised woodland fire control system several months ago.
Environmentalists say the number of personnel employed to spot wildfires has been slashed by over a half.
This has greatly contributed to the massive loss of forests and wildlife around the capital, Mikhail Kreyndlin, head of Greenpeace Russia's programme on specially protected natural areas, told BBC News.
"If bigger animals are able to escape the fires, smaller ones, including insects, have perished," he said.
Smog has also been a major issue, he added, especially for birds.
"Birds have very intensive breathing, and such extreme levels of air pollutants have definitely affected them," he said, explaining that it was possible for birds to basically drop dead from the skies.
Dr Kokorin said global warming creates another problem.
"If it gets warmer in the winter and in the spring and hotter in the summer, fauna changes.
"For example, we have never had as many regions in Russia affected by malaria, and the same goes for ticks carrying encephalitis. This is because winters are becoming much warmer, and less and less of these organisms die during the freezing periods."
There have also been reports of freshwater jellyfish, commonly found in warm lakes and rivers in North America, Europe and Asia, fished out from the abnormally warm waters of the Moscow river.