Temperatures in the Russian capital hit 37.7 degrees Celsius (99.86 Fahrenheit), beating the previous record set on July 26, said the Fobos forecasting center which provides weather data for the country's top media outlets.
At Domodedovo airport outside Moscow, temperatures soared to 38.7 Celsius (101.66 Fahrenheit), Fobos said.
The adverse effects of the severe heat which has been terrorizing Muscovites since late June are aggravated by heavy smog which blankets the city of over 10 million and is caused mainly by burning peat in forests surrounding Moscow.
Russia's chief lung doctor Alexander Chuchalin warned on Wednesday that due to a large concentration of toxins in the air walking in the streets of Moscow is like smoking two packs of cigarettes every few hours.
Mineral water and soft drinks sell like hot cakes in Moscow, while many pharmacies have run out of oxygen sprays.
Elsewhere in Russia, a drought unseen for all 130 years of weather observation has killed crops on an area the size of Hungary, leading the government to impose a state of emergency in 23 regions.
But after suffering from the suffocating heat for nearly six weeks, Muscovites may finally get a breather on Friday when a cold atmospheric front is expected to bring extreme temperatures down to above 30 degrees Celsius, Fobos said.
