The skeptic in me always wonders just how the blood "knows" when to melt and how it really does. That kind of stuff is fascinating even on a purely factual basis, but then I am a heretic.
I do agree, it's got to be a good sign.
It's an act of God. There have been occasions where the blood didn't liquify, and disasters strike shortly afterwards. The lack of liquification on the feast day is an omen.
That's the second time you've said that you're a "heretic." Don't be self-conscious. You're closer to Catholics than you think. ;-)
The annual liquefaction of this blood is not an "article of faith," and although those who are devoted to this find consolation in it --- well and good --- still, nobody is obliged to believe in it on pain of heresy.
So just a pious fraud.
However, I remember once when the blood didn't turn liquid, and there was a nearby disaster due to a volcano...I think it was during the 1983 problems...see LINK
So maybe
A>it's a pious fraud that can predict the future, or maybe
B>God is using this pious fraud to warn the people of Naples about their volcano, or maybe
C>it's just a coincidence, or maybe
D>there is a scientific reason that when the volcano is active the chemicals don't turn liquid.
Take your choice.
I'm a skeptic, but believe in God. I figure the answer is either B or D...