Summer in St Petersburg is moderately warm. There is less rainfall in July than in June or August, while August is almost 2 C cooler than July. This can vary, of course, with some years bringing higher temperatures in June than in July or August.
Saint Petersburg is famous for its White Nights. They begin after the 10th of June; by this time the sun sets only 9 degrees below the horizon. By June 21 the length of the day has increased to 18 hours 53 minutes.
And nowhere is the return of summer hailed with more delight than in St. Petersburg. It is even officially celebrated by the annual ceremony of opening the navigation of the Neva. As soon as the ice has moved away seaward the first vessel to be launched on the stream is always that of the Commandant of the fortress, who is rowed across the river in his state barge to the Palace under a salute from the guns on the ramparts.
St. Petersburg, George Dobson, 1910
During White Nights, when the faint twilight takes the place of night darkness (and then even not for more than 30-40 minutes), the streets, squares, and embankments acquire a unique charm. The White Nights come to an end around July 2.
Summer in St Petersburg, Summer Palace:
Summer In St Petersburg, Griboedov Canal:
Summer In St Petersburg, Catherine Palace: