Tourist season in St.Pete starts within the summer. Although you need to keep in mind that ‘the summer’ here usually lasts for two weeks and nobody knows when to expect it. The rest of ‘the summer’ differs from its seasonable neighbors in the fact that you have no need to wear you wool socks. June in St.Pete gives a start to white nights during which you have an opportunity to see some of the most beautiful drawbridges in action (or mighty cable-stayed bridge if you need to cross the Neva at night) and make a no-red-eyes photo on the city streets at 4 a.m. In autumn St.Pete reminds its locals of Pushkin (because he used to write a lot about golden leaves and such); in winter it’s spruce and full of romantic lights that are reflected in mysteriously dark waters of rivers and canals.
By the way, I highly recommend to not forget about the wild side of St.Pete; you should definitely take a look at the famous well-yards (yards so narrow they look more like wells), go to legendary trash bars on Dumskaya Street, walk up to the roof at the center of the city or go to the jazz session.
I also can give you a tip on where to find some great apartment to rent, some awesome restaurant to visit or a good guide that will attentive to you to follow. Do you want something on the more modest side? Not a problem!
I know couple of great hostels; my old friends keep one. Moreover, I’m perfectly fine with meeting you at the airport or at the train station myself, or just give you a reasonably priced taxi service number.