The mercury in the capital topped 31 degrees Celsius (87.8 degrees Fahrenheit) by midday, beating the previous record for May 31 of 30.6 degrees Celsius (87 degrees Fahrenheit) set in 1889, the service said.
As a result of the heat, many Moscow stores have begun running out of cold drinks, especially kvas, a traditional Russian brew, which has been in demand this past week, along with ice cream.
Some stores have reportedly been taking advantage of the situation to gouge customers, often doubling the prices they charge for cold drinks.
However, according to Lyudmila Korzhneva, a deputy head of Moscow's retail oversight body, nothing can be done because storeowners are free to charge whatever price they feel the market will bear.
"We are not undertaking any inspections to check for price inflation on seasonal products. In this country we have laws guaranteeing the freedom to set prices," she said.
"On the other hand, a smart storekeeper will look not to raise prices but to increase sales, because if he raises his prices today, maybe tomorrow customers will think twice before returning to his store," she said.