I am going to the 2015 Italian GP this year and spending a few days in Milan either side.
When looking at accommodation in a guide book I noticed mention of Expo 2015 which is also being hosted by Milan between 1st May and 31st October. It’s a huge Energy and Food fair that they are building a massive park and transport links for.
This is affecting both room price and room availability.
For those wanting to stay in and around the Milan area I would book up sooner rather than later if you can…some hotels are already sold out.