There is no specific off season in York and it is filled with tourists all round the year. However, spring and summers are considered to be the busiest and costliest period as it is time for various major events across the city. If you do not like travelling in crowds, it will be advised to avoid the weekends in July and August. Though its bit cold during the autumn and winters, that is the main time when York comes to life. Snowfalls and Christmas is a really good experience in York.