For those of us who work in emergency planning, this is a subject of constant debate. I’m lucky, I only have to worry about the people who work in my organisation (and only in my region) but even then, timings of warnings and briefings, particularly for adverse weather events, keeps me up at night. You’ve got to go early enough to inform and allow people to organise themselves or change their behaviour but not so early that the warnings become background noise, or worse, become redundant because of changing circumstances. The US National Weather Service have done a huge amount of work on this and there are lots of interesting papers on the subject out there. FWIW, I’m getting briefed at 11:00 am this morning, but we issued our first advisory last night. I expect to be very busy this afternoon and tonight.