A mandatory evacuation order for zone A in Hillsborough was effective 2pm Monday. The airport is located within zone A. Tropical storm force winds are anticipated to arrive not long after 2pm based on current information. Keeping the airport open until mid-day Tuesday puts workers who live across the bay at risk. Bridges begin shutting down when winds get to a certain speed. It also puts airline assets at risk should an aircraft go mechanical Tuesday morning. Where would those passengers go? Hotels near the airport? Those are in evacuation zones A and B.

So in a nutshell it makes sense the city decided to close the airport at midnight given too many moving parts, any of which could go wrong if the weather goes south earlier than expected on Tuesday. They are allowing late inbounds tonight to land and deplane. But the aircraft are being ferried out ASAP.