The Cinque Terre is uncomfortably busy from June to early September, and Corniglia — the smallest of the five villages — feels the crowds disproportionately on its narrow main street. The best months are April, May, late September and October: warm enough to swim, the trails open, the light gentle on the terraces, and the trattorias willing to take a walk-in booking.
Winter (November to March) is genuinely quiet. Many restaurants close, the ferry stops running, and the weather is unpredictable, but you can have the village more or less to yourself and the views in clear winter air are sharper than at any other time of year. Bring a jumper — the wind off the sea is cold.
The grape harvest in September is the most photogenic moment of the year, with the vineyards above the village busy and the small monorails carrying baskets of grapes down the terraces.