Autumn ice on the Neva is strong enough. On the case of a very early frost Neva wrote in a letter to the mother Pavel Tretyakov – the founder of the Tretyakov Gallery – October 1852: "19 this month went to on the Neva Peter and Paul Fortress "The observation was done in two days after the Neva River rose. The latest freezing river marked on Jan. 20, 1952. The earliest opening – March 16, 1938 at the latest – May 12, 1810. In our time Neva freezes later and breaks up earlier than 100-150 years ago, because of the heat emitted by the big city. On the Neva River is two spring break-up. Breaks up the river more often in early April, when the river is ice. This is not very spectacular. A few days later the river is cleared. After a week or two warm weather gives way to cold, and the river suddenly appear big white ice floes – Ladoga moved. Lake Ladoga is revealed later Neva – that's why there are two ice flows. Ice of Lake Ladoga driven cold northeasterly winds, and they do not and ice from the lake into the Neva will not go – this happens in some years. The ice of Lake Ladoga via the Neva River can not get through. It is estimated that the river falls 1-2% of the ice. To "drive" across the river the whole Ladoga ice, it would take two years.