Milan, depending on how you want to tour the city, is virtually visitable all the year.

In autumn, the weather is warm/cool, and in later months can be quite rainy and foggy. At this time of the year, the city's inhabitants are very busy with work, so, the only people you're likely to see wandering around are tourists. All the major venues and shops are opened, since it is the working part of the year.

In winter, the city can become very, very cold (often below or around zero degrees centigrade), and the weather is usually foggy and rainy if not snowy. However, the city, in the few weeks before Christmas, becomes delightful to visit - the main sights are all illuminated by stunning lights, a huge Christmas tree is set up in front of the Duomo, vendors and markets can be found everywhere, many shop and display windows are decorated and the streets become bustling with locals and tourists alike. However, the only downside is that it can become extremely crowded, noisy and busy.

In spring, the weather is similar to that of autumn. People go back to work, and the atmosphere becomes more quiet, yet serious unlike that of the winter. Parks become nice to visit, as trees blossom. The city is also quite nice to visit at Carnival, where people dress up and celebrate, and during Easter, where there are special services held in churches and some special events.

In summer, Milan can become extremely hot and humid, with the odd powerful rainstorm here and there. Whilst in July, apart from the weather, most shops remain open, in August, as many locals go off to take their summer holidays, many businesses and venues shut down (with the notice Chiuso per ferie, or shut down for vacation). The city may become quite empty with the odd tourist strolling around, and with several of the main sights shut down. Despite it's not the best time for shopping and the weather's not at all times very pleasant, it's good if you want to enjoy the city to yourself when it's quiet, and maybe want to stroll around, sipping at the odd open bar or at an ice cream, or walking in a silent park. Despite many businesses shut down, some still do remain open, and you will still be able to find some open shops, restaurants and museums.