The success of Russian harvests often hinged on favourable weather conditions. Russian farmers experienced droughts every five to seven years, each producing crop failures, drops in yield and food shortages. These droughts were a significant causal factor of the Great Famine. Russia’s total crop yield in 1921 was about half that of 1913, the last year of peace. Worse still, the winter of 1916-17 was exceptionally cold, even by Russian standards (which, if anyone has been to Russia, is seriously cold). This caused yet more famine as crops failed.