All of the world's "great" civilizations come from places with strong seasonality. The ones that didn't have winters had flooding seasons and dry seasons. Some of them had both. It also doesn't need to be bitterly cold for winter to have an effect on crops.

Sumeria and Egypt both had seasonal flooding. Italy and Greece have winters that are cold enough to disrupt agriculture. The Aztecs and Mayans had seasonal floods. The ancient Chinese empires had both. Japan has winters. The list goes on.