Most of Russia has a continental climate - the winters are bone chilling and the summers can be boiling.
The swings are most extreme in southern and central Siberia, but even in Moscow temperatures can range from -30 to 30 Celsius (-20 to 100 Fahrenheit). See Measurements for information on converting temperatures.
The Black Sea coast and its resort communities tend to have the least swing.
Late spring, early summer and the fall are good times to visit. During the hot summer months of July and August cities shut down as locals head to the countryside to live off the land at their dachas.
In the beginning of September the ballets and the operas start back up and the cities come to life again. (The performing arts season runs from about September to May, although there are occasional shows in the summer, especially during St. Petersburg's White Nights Festival in June.)
The first real cold hits Moscow and St. Petersburg sometime in November and there's usually snow on the ground from December through April.
If you're prepared for the cold, Russia is often at its most beautiful under a blanket of snow. Winter is also the peak of the theater season and generally has fewer tourists. Steer clear of the mud and slush that covers the country during the spring thaw (April to May) and late fall.