Severe weather in Sicily can escalate fast - I remember one time a friend's family there got caught in what started as heavy rain and turned into something much more dangerous within an hour. The infrastructure in some areas isn't always equipped to handle extreme weather events, so when something like this hits, the damage and disruption can be really significant.
Right now you're dealing with a situation where local authorities and emergency services are your most reliable source. Italian national weather services (Protezione Civile) and regional Sicilian sources will have the latest on what's happening, where it's safe, and what precautions people should take. If you have people in that region, direct contact with them or checking their regional news outlets beats anything I could tell you from here - conditions on the ground change constantly during active severe weather, and what's accurate in one moment might be outdated minutes later.