The weather in Sicily in April and September is really nice. Day time temperatures range between 20 and 24 °C all around the island. The temperature increases slightly as you travel to the southern part of the island. Evening temperature range from 10 to 12 °C so you will need a light jacket in your gear. The island gets between 20 and 30 mm (about 3/4 to 1 inch) of rain in the months of April and September. Most of the rainfall occurs in the late afternoon. The humidity is about 68 to 72% all around the island. Winds are between 5 and 8 knots. As the land heats up during the day the air heats up also. It heats up more over the land than the sea and so the hot air over the land rises drawing air in from over the water onto the land. This creates a pretty steady breeze from off the water every day. In the evening the process is reversed. This means that almost everywhere on the island we will be riding into a nice off shore breeze. I have set up links to "The Euro Weather" web site so you can check the weather around the island in greater detail.