'You better open it, Ron,' said Neville, in a timid whisper.'It'll be worse if you don't. My gran sent me one once, and i ignored it and -' he gulped, 'it was horrible.'
I don't really think it can be more horrible then when you open it , but what do you think will happen if you don't open a howler?
it smolders and explodes, then you have to deal with the screaming anyway on top of that...
I think it's covered in OotP... Petunia didn't open her howler...
"Open it!" Harry urged her. "Get it over with! It'll happen anyway-" "No --" Aunt Petunia's hand was trembling. She looked wildly around the kitchen as though looking for an escape route, but too late -- the envelope burst into flames. Aunt Petunia screamed and dropped it. An awful voice filled the kitchen, echoing in the confined space, insuing from the burning letter on the table. "REMEMBER MY LAST, PETUNIA."
I don't remember what book it was in but I am pretty sure that it is stated that if you don't open one it blows up and the magically magnified voice rants on anyway.
Oh yeah I think I remember, Didn't Percy get one in GoF that he didn't open and it blew up his desk?
Oh, yeah, I had forgotton about the howlers sent to Percy's work after the World Cup... the one of Petunia's is, I think, the only unopened howler we actually see, though.
I wonder whether the voice gets louder the longer its left too...because just an explosion like the one described doesn't seem that much worse than what you get if you open it straight away.....
I remember that too, I think it's just mentioned in passing, so it's not like the most important thing...I assumed it just got louder than it would be normally if you ignored it.
I think it might have been the howler Neville got from his gran after he lost the password in PoA... dont' know for sure, don't feel like looking it up... didn't he run out of the Great Hall, and it exploded in the Entrance Hall, louder than usual?
I wonder how they do Howlers....I mean...it cant be on a timer from when it was written so it must be from when the person receives the howler...I wonder how many times the Howler has got it wrong though and exploded in transit so that only a very singed and freaked out bird arrives at the destination.....
oh and another thought...sorry this only occured after submitting post....if that does happen I wonder if the owls get danger money...I mean, does it cost more to post a howler by mail (if you use the post office in Hogsmeade say) than a normal letter as insurance against the howler oppening early and terrifying the poor owl.....
I don't think the owls get paid. The owl that delivers the paper does, but it doesn't go to the owl, it goes to the paper. Hedwig gets damaged while on business, and she gets a little TLC and goes back to work.